||Brentano introduces the notion of intentionality in Chapter 1 of Book II of Brentano 1874; his 1911 appendix on the notion is important (included in the same English edition). From Brentano, the notion propagated into all branches of the Brentano School, but most prominently through the phenomenological movement (see especially Husserl 2012). Other important contributions by Brentano's students include Twardowski 1977 and Meinong 1904. The notion is brought into analytic philosophy and regimented by Chisholm in Chisholm 1957, and later becomes central to philosophy of mind (see, e.g., Searle 1983). For an interpretation of Brentanian intentionality as a relation to immanent objects, see Brandl 2005; for an interpretation of it as not really a relation, see Chisholm 1988 (and, relatedly, Crane 2006). For a recent discussion of its connection to the notion of phenomenal intentionality, see Dewalque 2013. For discussion of Brentano's claim that intentionality is the mark of the
mental, see Crane 1998 and Kriegel 2017.