International Journal of Academic Information Systems Research (IJAISR) ISSN: 2000-002X Vol. 2 Issue 2, February – 2018, Pages: 8-18 www.ijeais.org/ijaisr 8 Excel Intelligent Tutoring System Sabreen Refat Qwaider, Samy S. Abu-Naser Department of Information Technology, Faculty of Engineering & Information Technology, Al-Azhar University, Gaza, Palestine Abstract: The invention of technology and its entry into many fields facilitated many things. For example, there were smart systems that were based on diagnosing diseases, organizing traffic, and teaching students in schools. These days, relying on traditional education (classroom lectures, texts, and individual assignments) at schools is no longer the only and best solution for educating students, increasing their culture and keeping them up to date in life. E-learning was an ideal solution, based on Lifelong learning implies lifelong education, artificial intelligence has an imprint in this by developing systems depend on one or more teacher for each student. In this paper, Intelligent Tutoring System Builder explains in terms of the meaning, key components and the integration between them. In order to implement this system, we had a smart Excel education system called Excel Intelligent Tutoring System, which aimed at novice students as users, and teachers as an exhibitor of educational material, with a simple explanation of how to use and benefit from the system. At the end, a system evaluation presentation was accepted as the basis for a long-term education project. Keywords: Excel, intelligent tutoring system, learning, ITS, e-learning, Intelligent Tutoring, Knowledge Module, Teaching Strategy, Tutor Module, Student's Learning Style 1. INTRODUCTION Knowledge development for teaching does not depend only on traditional teaching. It has merged with advanced technology to create a new science called Intelligent Tutoring Systems (ITS). These systems are based on Artificial Intelligence in education as main concept such it displays differential tutorials as an expert teachers, for students with different education levels. One of these tutoring systems are Intelligent Tutoring System Builder (ITSB) tool which is an authoring tool collecting three components: AI, Cognitive science and the internet to be designed and developed to aid teachers in constructing intelligent tutoring systems in multidisciplinary fields [1] . ITS delivers different exiting or traditional systems, adapting teaching methods from previous human-teachers knowledge, to produce an effective tutorials(text, sound and video materials) with examples, questions(certain answers or article questions) and tests at each level from beginner to advanced one. In addition, it gives hints and corrects the false answers. One person or a collaborative team can use it so that it considers as one-to-one or many-teachers experience to one student from teaching side and one-tomany students from students side. 2. LITERAL REVIEW There is no determined domain or relative type for ITS. The earliest system was Pascal's Calculator as mechanical intelligent systems created at 17th century by Blaise Pascal, which was capable of doing calculations using mathematical functions. At that time, Gottfried Leibniz was trying to apply rules and logic on the computer that facilitated the rapid evolution of computers. Through the work of Leibniz and other philosophers and developers, private tutoring systems have now expanded to include multiple types, and have entered many fields as SHERLOCK in industry to train Air force technicians, and CODES as a Web-based environment for music prototyping and at trade discipline Pascal was a strong system with continuous development until now. The inventions and innovations in this open field have also extended to medicine with CARDIAC tutor to support students, and medicine trainers at cardiac arrest problems using variety of treatment steps. Despite all this, the share of the field of education was the largest, as it included the education of illiterate people, students of all levels of school, university students and even post-university practitioners as mentioned in the CARDIAC system. Some of them: ANIMAL WATCH to teach student from 10 to 12 years-old, how to deal with mathematical problems according with text questions about endanger animals. PAT (PUMP Algebra Tutor or Practical Algebra Tutor) was developed by the Pittsburgh Advanced Cognitive Tutor (PACT) Center to help students at 12-15 years old successfully use algebra to solve problems and to see its relevance in both academics and the workplace where it represents the information in various ways (text, tables, and graphs). As the previous tutors, there are ACTIVEMATH and MATHEMATICS TUTOR related to mathematical problems but at various study levels. In another field, such as the difficulties in reading texts for children, the tutoring may not interrupt him while reading using a microphone until the end of sentence and then it International Journal of Academic Information Systems Research (IJAISR) ISSN: 2000-002X Vol. 2 Issue 2, February – 2018, Pages: 8-18 www.ijeais.org/ijaisr 9 correct the pronunciation [1] . While enhancing the student's perusing and reading comprehension, REALP was prepared to give them a series of exercises based on purposed vocabulary after reading lessons [57] . On the other hand, university students have some of these useful tutors for example: SQL-Tutor to retrieve data from databases using SELECT statement, COLLECT-UML is paired student tutor to work collaboratively on UML class diagrams and provides feedback at domain level [57] . The integration of physics with technology was evident in ANDES TUTOR that intended for use in universities, high schools and courses to help the user to solve physics problems instead of using papers [3]. In addition at geometric GEOMETRY EXPLANATION or GEOMETRY COGNITIVE TUTOR is one of the top existing tutors for solving geometry problems and providing support as hints and feedback to land at more precise mathematical explanations [56] . There are many tutors available in different fields such as programming languages, Mathematics, education, health, and security[44-53]. In this paper, we used Intelligent Tutoring System Builder to set up Intelligent Tutoring System to learn Excel. 3. TUTOR STRUCTURE ITSB was designed using Delphi Embarcadero XE8 2015Error! Reference source not found.with Arabic and English languages presentation. It is used at two ways: Teacher staff for adding the education material, examples, illustrative pictures, videos, and questions, and Student form for studying the lessons at every level, and response by answering the questions. Tutoring systems are generally shared at some (main) features and different at others as shown in Figure 1. Excel Tutoring System has: student model, domain model, teaching model, and user interface model. Figure 1: Typical Architecture for Intelligent Tutoring System (ITS) 3.1 Excel Domain Model The domain has two targets, one for containing, arranging and organizing the lessons (Domain Organization Model), and the second is a store for the material taught by itself (Repository) Error! Reference source not found.. The teacher sets the lessons in a specific order in the "lessons" folder in the format of ".rtf". The tutor performs the rest of the tasks in terms of organization and shows them sequentially as appropriate to the user. The teacher then puts the questions and organizes them with specific difficulty levels and the system helps to link them to its lessons. Therefore, when the student answers a set of questions related to a specific lesson, and the tutor evaluates him/her, if he/she passes the trajectory (the limit of failure), he passes it to the next lesson. If not, it will force him/her to return to read the lesson again before going to the next lesson. Excel tutorial covers the following subjects:  Introduction to Microsoft Excel 2013.  Transporting between Cells.  Cleaning Data.  Data Types.  Auto fill features.  Excel Charts and Charts.  Pivot Tables and Pivot Charts. 3.2 Excel Student Model This section is specific to the student but is also related to the domain model. Each student has his or her own profile including the student's name, student's number, specialization (Major), general average (GPA), degree of difficulty, current grade, current lesson, question number, and overall score. All of this information is kept confidential, and is used to track the student and measure the extent of his progress each time from the previous time. It focuses on the development of educational tutorials, with knowledge of the student's situation in terms of concentration and emotion, to bind to the ability to answer questions with different degrees of difficulty and improve the performance the next time. 3.3 Excel Pedagogical Module In fact, students do not learn at the touch of a button, so the old teaching theory that depends on feeding, receiving, then memorizing has not worked and does not consolidate information in the minds of students to take advantage of it for the long term. Therefore, the Excel Tutoring System has never relied on this theory at all, but it uses advanced theories and methods of learning that focus on understanding and absorption the International Journal of Academic Information Systems Research (IJAISR) ISSN: 2000-002X Vol. 2 Issue 2, February – 2018, Pages: 8-18 www.ijeais.org/ijaisr 10 student of the information and explaining it in different ways and means that make it easier to remember. The system does not interrupt the student during the stage of understanding or solving the questions, even if the answer is wrong, however it presents the correct answer to him after the end of the solution, and shows help if needed. The structure of student steps in ITS shown in Figure 2. Figure 2: Student steps in ITS 3.4 Excel user Interface User interfaces are an important and essential part of the Excel learning system. There are two types of user interfaces: teacher interfaces and student interfaces. Each of them sees facades that differ from each other. The teacher is the ground of the system as the interface used is empty shell. The teacher will place basic system data such as the name of the system, the name of the teacher or the author of these lessons, a background image of the system's main interface, the language of the system (Arabic-English) or vice versa , the colors to be used in the system, the font size, questions, buttons, and others. The teacher also registers a new student and puts all of his / her data mentioned above in (Excel Student Model). In addition, the teacher sets lessons and questions with the characteristics and order mentioned in (Excel Domain Model) so that the system will then use his theories of education as mentioned in (Excel Pedagogical Module). Thus, the system becomes an independent field for this teaching material, as shown in Figure [3, 4, 5, 6, 7, 8]. Figure 3: Admin Login Interface International Journal of Academic Information Systems Research (IJAISR) ISSN: 2000-002X Vol. 2 Issue 2, February – 2018, Pages: 8-18 www.ijeais.org/ijaisr 11 Figure 4: Updating features Interface for ITS screens Figure 5: Updating features for Main Interface International Journal of Academic Information Systems Research (IJAISR) ISSN: 2000-002X Vol. 2 Issue 2, February – 2018, Pages: 8-18 www.ijeais.org/ijaisr 12 Figure 6: Inserting Lesson Interface Figure 7: Updating Lesson Interface International Journal of Academic Information Systems Research (IJAISR) ISSN: 2000-002X Vol. 2 Issue 2, February – 2018, Pages: 8-18 www.ijeais.org/ijaisr 13 Figure 8: Student Registration Interface As for the student interface, it displays a screen to display the lessons, and other examples either in the form of illustrations or videos. There is also a special interface for questions and exercises, followed by a destination to present the result of evaluating student performance, as shown in figure [9, 10, 11, 12, 13]. Figure 9: Student Login Interface International Journal of Academic Information Systems Research (IJAISR) ISSN: 2000-002X Vol. 2 Issue 2, February – 2018, Pages: 8-18 www.ijeais.org/ijaisr 14 Figure 10: Lessons Interface Figure 11: Questions Interface International Journal of Academic Information Systems Research (IJAISR) ISSN: 2000-002X Vol. 2 Issue 2, February – 2018, Pages: 8-18 www.ijeais.org/ijaisr 15 Figure 12: Estimation-Passing Level 1Interface Figure 13: Estimation-Failure at Level 2Interface 4. EVALUATION OF THE EXCEL ITS The evaluation of the system was based mainly on the views of both the human teachers of Excel and the students who did not have any previous experience of the Excel. They were asked several questions in terms of ease of dealing with the system, efficiency, and in terms of educational material used in the explanation if it is clear as required for novice students, the examples used are clear, and if the questions used meet the purpose of establishing the information in mind. Also if there are any suggestions for development of the program. International Journal of Academic Information Systems Research (IJAISR) ISSN: 2000-002X Vol. 2 Issue 2, February – 2018, Pages: 8-18 www.ijeais.org/ijaisr 16 The answers were as in the following table for both the first class (Excel's teachers) and the second class (junior students), as shown in Table [1]. Table 1: The result of the evaluation of Excel ITS's user Category Excel Teachers Novice Students Tutoring System Ease of dealing with the system 69% 69% The system's flexibility 92% 94% Education materials Tutorial is appropriate and clear 90% 90% Examples are easy to understand and can be applied 93% 92% Questions ranging in degree of difficulty 88% 89% Opinions for Development We strongly support the program but want to have a pretest done before to make the system suitable for students with prior experience moving directly to their level. We have a greater incentive to learn Excel. The system is interesting and easy to deal with, although we wish there is a panel like Excel in the same program to apply examples instead of moving between the system and the program. 5. CONCLUSION In this research paper, the intelligent tutoring systems (ITS) were generally clarified and their internal structure, with a clear demonstration of the function of each system's part, for both tutoring users (the teacher and the student). After that, we have dedicated the system to Excel's intelligent tutoring system, the topics covered in it, and how the user categories of the system can be used, while making use of it effectively. In addition, screenshots of the system were used to illustrate this. Finally, the opinions of teachers and students were presented in detail and their suggestions for development. REFERENCES [1] Abu Naser, S. S. (2016). ITSB: An Intelligent Tutoring System Authoring Tool. Journal of Scientific and Engineering Research, 3(5), 63-71. [2] Qwaider, S. R., & Abu Naser, S. S. (2017). Expert System for Diagnosing Ankle Diseases. International Journal of Engineering and Information Systems (IJEAIS), 1(4), 89-101. [3] AbuEl-Reesh, J. Y., & Abu Naser, S. S. (2017). An Expert System for Diagnosing Shortness of Breath in Infants and Children. International Journal of Engineering and Information Systems (IJEAIS), 1(4), 102-115. [4] Elnajjar, A. E. A., & Abu Naser, S. S. (2017). DESTutor: An Intelligent Tutoring System for Teaching DES Information Security Algorithm. International Journal of Advanced Research and Development, 2(1), 69-73. [5] Al Rekhawi, H. A., Ayyad, A. A., & Abu Naser, S. S. (2017). Rickets Expert System Diagnoses and International Journal of Academic Information Systems Research (IJAISR) ISSN: 2000-002X Vol. 2 Issue 2, February – 2018, Pages: 8-18 www.ijeais.org/ijaisr 17 Treatment. International Journal of Engineering and Information Systems (IJEAIS), 1(4), 149-159. [6] Almurshidi, S. H., & Abu Naser, S. S. (2017). Design and Development of Diabetes Intelligent Tutoring System. EUROPEAN ACADEMIC RESEARCH, 6(9), 8117-8128. [7] Abu Ghali, M. J., Mukhaimer, M. N., Abu Yousef, M. K., & Abu Naser, S. S. (2017). Expert System for Problems of Teeth and Gums. International Journal of Engineering and Information Systems (IJEAIS), 1(4), 198-206. [8] Al-Bayed, M. H., & Abu Naser, S. S. (2017). An intelligent tutoring system for health problems related to addiction of video game playing. International Journal of Advanced Scientific Research, 2(1), 4-10. [9] Hamed, M. A., & Abu Naser, S. S. (2017). An intelligent tutoring system for teaching the 7 characteristics for living things. International Journal of Advanced Research and Development, 2(1), 31-45. [10] Almurshidi, S. H., & Abu Naser, S. S. (2017). Stomach disease intelligent tutoring system. International Journal of Advanced Research and Development, 2(1), 26-30. [11] El Agha, M., Jarghon, A., & Abu Naser, S. S. (2017). Polymyalgia Rheumatic Expert System. International Journal of Engineering and Information Systems (IJEAIS), 1(4), 125-137. [12] Khella, R. A., & Abu Naser, S. S. (2017). Expert System for Chest Pain in Infants and Children. International Journal of Engineering and Information Systems (IJEAIS), 1(4), 138-148. [13] Akkila, A. N., & Abu Naser, S. S. (2017). Teaching the right letter pronunciation in reciting the holy Quran using intelligent tutoring system. International Journal of Advanced Research and Development, 2(1), 64-68. [14] AbuEloun, N. N., & Abu Naser, S. S. (2017). Mathematics intelligent tutoring system. International Journal of Advanced Scientific Research, 2(1), 11-16. [15] Bakeer, H. M. S., & Naser, S. S. A. (2017). Photo Copier Maintenance Expert System V. 01 Using SL5 Object Language. International Journal of Engineering and Information Systems (IJEAIS), 1(4), 116-124. [16] Nabahin, A., Abou Eloun, A., & Abu Naser, S. S. (2017). Expert System for Hair Loss Diagnosis and Treatment. International Journal of Engineering and Information Systems (IJEAIS), 1(4), 160-169. [17] Al-Nakhal, M. A., & Abu Naser, S. S. (2017). Adaptive Intelligent Tutoring System for learning Computer Theory. EUROPEAN ACADEMIC RESEARCH, 6(10), 8770-8782. [18] Abu Hasanein, H. A., & Abu Naser, S. S. (2017). An intelligent tutoring system for cloud computing. International Journal of Academic Research and Development, 2(1), 76-80. [19] Alhabbash, M. I., Mahdi, A. O., & Abu Naser, S. S. (2016). An Intelligent Tutoring System for Teaching Grammar English Tenses. EUROPEAN ACADEMIC RESEARCH, 6(9), 7743-7757. [20] Alawar, M. W., & Abu Naser, S. S. (2017). CSSTutor: An intelligent tutoring system for CSS and HTML. International Journal of Academic Research and Development, 2(1), 94-98. [21] Al-Bastami, B. G., & Abu Naser, S. S. (2017). Design and Development of an Intelligent Tutoring System for C# Language. EUROPEAN ACADEMIC RESEARCH, 6(10), 87-95. [22] Hilles, M. M., & Abu Naser, S. S. (2017). Knowledge-based Intelligent Tutoring System for Teaching Mongo Database. EUROPEAN ACADEMIC RESEARCH, 6(10), 8783-8794. [23] Al-Hanjori, M. M., Shaath, M. Z., & Abu Naser, S. S. (2017). Learning computer networks using intelligent tutoring system. International Journal of Advanced Research and Development (2), 1. [24] Aldahdooh, R., & Abu Naser, S. S. (2017). Development and Evaluation of the Oracle Intelligent Tutoring System (OITS). EUROPEAN ACADEMIC RESEARCH, 6(10), 8711-8721. [25] Shaath, M. Z., Al-Hanjouri, M., Abu Naser, S. S., & Aldahdooh, R. (2017). Photoshop (CS6) intelligent tutoring system. International Journal of Academic Research and Development, 2(1), 81-87. [26] Mrouf, A., Albatish, I., Mosa, M., & Abu Naser, S. S. (2017). Knowledge Based System for Long-term Abdominal Pain (Stomach Pain) Diagnosis and Treatment. International Journal of Engineering and Information Systems (IJEAIS), 1(4), 71-88. [27] Naser, S. (2009). Evaluating the effectiveness of the CPP-Tutor an intelligent tutoring system for students learning to program in C++. Journal of Applied Sciences Research, 5(1), 109-114. [28] Mahdi, A. O., Alhabbash, M. I., & Abu Naser, S. S. (2016). An intelligent tutoring system for teaching advanced topics in information security. World Wide Journal of Multidisciplinary Research and Development, 2(12), 1-9. [29] Al Rekhawi, H. A., & Abu Naser, S. (2018). An Intelligent Tutoring System for Learning Android Applications Ui Development. International Journal of Engineering and Information Systems (IJEAIS), 2(1), 114. [30] Albatish, I., Mosa, M. J., & Abu-Naser, S. S. (2018). ARDUINO Tutor: An Intelligent Tutoring System for Training on ARDUINO. International Journal of Engineering and Information Systems (IJEAIS), 2(1), 236-245. [31] Mosa, M. J., Albatish, I., & Abu-Naser, S. S. (2018). ASP. NET-Tutor: Intelligent Tutoring System for leaning ASP. NET. International Journal of Academic Pedagogical Research (IJAPR), 2(2), 1-8. [32] AbuEl-Reesh, J. Y., & Abu-Naser, S. S. (2018). An Intelligent Tutoring System for Learning Classical Cryptography Algorithms (CCAITS). International Journal of Academic and Applied Research (IJAAR), 2(2), 1-11. [33] Abu Ghali, M., Abu Ayyad, A., Abu-Naser, S. S., & Abu Laban M. (2018). An Intelligent Tutoring System for Teaching English Grammar. International Journal of Academic Engineering Research (IJAER), 2(2), 1-6. [34] Marouf, A., Abu Yousef, M. K., Mukhaimer, M. N., & Abu-Naser, S. S. (2018). An Intelligent Tutoring System for Learning Introduction to Computer Science. International Journal of Academic Multidisciplinary Research (IJAMR), 2(2), 1-8. [35] Abu Naser, S. (2008). An Agent Based Intelligent Tutoring System For Parameter Passing In Java Programming. Journal of Theoretical & Applied Information Technology, 4(7). [36] Abu Naser, S. (2008). JEE-Tutor: An Intelligent Tutoring System for Java Expression Evaluation. Information Technology Journal, Scialert, 7(3), 528532. International Journal of Academic Information Systems Research (IJAISR) ISSN: 2000-002X Vol. 2 Issue 2, February – 2018, Pages: 8-18 www.ijeais.org/ijaisr 18 [37] Abu Naser, S. S. (2001). A comparative study between animated intelligent tutoring systems AITS and video-based intelligent tutoring systems VITS. Al-Aqsa Univ. J, 5(1), 72-96. [38] Abu Naser, S. S. (2006). Intelligent tutoring system for teaching database to sophomore students in Gaza and its effect on their performance. Information Technology Journal, 5(5), 916-922. [39] Abu Naser, S. S. (2008). Developing an intelligent tutoring system for students learning to program in C++. Information Technology Journal, 7(7), 1055-1060. [40] Abu Naser, S. S. (2008). Developing visualization tool for teaching AI searching algorithms. Information Technology Journal, Scialert, 7(2), 350-355. [41] Abu Naser, S. S. (2012). Predicting learners performance using artificial neural networks in linear programming intelligent tutoring system. International Journal of Artificial Intelligence & Applications, 3(2), 65. [42] Abu Naser, S. S. (2012). A Qualitative Study of LPITS: Linear Programming Intelligent Tutoring System. International Journal of Computer Science & Information Technology, 4(1), 209. [43] Mahmoud, Ahmed Y and Chefranov, Alexander G. (2009). Hill cipher modification based on eigenvalues hcm-EE,Proceedings of the 2nd international conference on Security of information and networks ACM, pp. 164167 [44] Ahmed, Y Mahmoud and Chefranov, Alexander. (2011). Hill cipher modification based on pseudorandom Eigen values HCM-PRE, journal of Applied Mathematics and Information Sciences (SCI-E), vol (8:2), pp. 505-516 [45] Mahmoud, Ahmed Y and Chefranov, Alexander G. (2010). Secure Hill cipher modifications and key exchange protocol, Automation Quality and Testing Robotics (AQTR), 2010 IEEE International Conference, vol 2, pp.1-6 [46] Doukhnitch, Evgueni and Chefranov, Alexander G and Mahmoud, Ahmed. (2013). Encryption Schemes with Hyper-Complex Number Systems and Their Hardware-Oriented Implementation, Theory and Practice of Cryptography Solutions for Secure Information Systems},vol 110, IGI Global [47] Mahmoud, AY and Chefranov, Alexander G. (2012). Secure hill cipher modification based on generalized permutation matrix SHC-GPM, journal of Information Sciences Letters, pp. 91-102 [48] Chefranov, Alexander G and Mahmoud, Ahmed Y. (2013). Commutative Matrix-based Diffie-Hellman-Like Key-Exchange Protocol, Information Sciences and Systems 2013, pp. 317-324,Springer, Cham [49] Mahmoud, Ahmed Y and Chefranov, Alexander G. (2014). A Hill Cipher Modification Based on Eigenvalues Extension with Dynamic Key Size HCMEXDKS, International Journal of Computer Network and Information Security, vol 6:5, Modern Education and Computer Science Press [50] Chefranov, Alexander G and Mahmoud, Ahmed Y. (2010). Elgamal public key cryptosystem and signature scheme in GU (m, p, n), Proceedings of the 3rd international conference on Security of information and networks, pp. 164-167, ACM [51] Mahmoud, Ahmed Yehya Ahmed. (2012). Development of Matrix Cipher Modifications and Key Exchange Protocol, Ph.D thesis, Eastern Mediterranean University (EMU) [52] Mahmoud, Ahmed Y. and Mahdi, Ali Osama. (2016). Comments On Multi-window Against Mobile Application Lock, Journal of Multidisciplinary Engineering Science Studies (JMESS), Vol 2:5, May – 2016, pp. 494-497, JMESS [53] Abdelwahed, Ann S. and Mahmoud, Ahmed Y. and Bdair, Ramiz A. (2017). Information Security Policies and their Relationship with the Effectiveness of the Management Information Systems of Major Palestinian Universities in the Gaza Strip, International Journal of Information Science and Management, vol 15:1, pp. 126. [54] Beverly Park Woolf. Building Intelligent Interactive Tutors Book. 2009. [55] Andestutor: http://www.andestutor.org/, date visited Dec. 26, 2017. [56] Essays: https://goo.gl/QJCJfR, date visited Dec. 26, 2017. [57] Wikipedia: https://goo.gl/PwqNKE, date visited Dec. 25, 2017. [58] https://goo.gl/HvWmqu, date visited Dec. 14, 2017. [59] https://goo.gl/jzxK7H, date visited Dec. 14, 2017. [60] https://goo.gl/uN2HG1, date visited Dec. 14, 2017. [61] https://goo.gl/jgdFz8, date visited Dec. 22, 2017. [62] https://goo.gl/M7v9BK, date visited Dec. 22, 2017. [63] https://goo.gl/PS8TSz, date visited Dec. 22, 2017. [64] https://goo.gl/Zpxn3E, date visited Dec. 28, 2017. [65] https://goo.gl/9sDJxz, date visited Dec. 30, 2017. [66] https://goo.gl/qhRj74, date visited Dec. 30, 2017. [67] https://goo.gl/YGvJ4h, date visited Dec. 30, 2017. [68] https://goo.gl/zyFKFX, date visited Dec. 30, 2017. [69] https://goo.gl/TJ53iu, date visited Dec. 30, 2017. [70] https://goo.gl/iDKNNz, date visited Dec. 30, 2017. [71] https://goo.gl/c2pMgp, date visited Dec. 30, 2017. [72] https://goo.gl/r1E4Ge, date visited Dec. 30, 2017. [73] Wikipedia: https://goo.gl/zcXwEv, date visited Dec. 30, 2017. [74] Wikipedia: https://goo.gl/vzg2HA, date visited Dec. 30, 2017. [75] Itstillworks: https://goo.gl/ZDM5oW, date visited Dec. 30, 2017.