||For Scheffler's use of the sense/reference distinction in relation to meaning variance and the comparability of theories, see Scheffler 1967. Hilary Putnam indicates how a causal theory of reference may be of use with respect to this issue in Putnam 1973. Arthur Fine raises problems about change of reference which seem to be ruled out by the causal theory in Fine 1975. Devitt provides general coverage of the topic, including some basis for a response to Fine in Devitt 1979. Kitcher also makes good suggestions about how to deal with the problem of reference change in Kitcher 1978. The problem of reference failure for theoretical terms within the context of the causal theory and reasons to move to a causal descriptive account are dealt with in Enç 1976, Nola 1980 and Kroon 1985. For an influential discussion of theoretical terms, see Lewis 1970. A very influential critical discussion of reference in relation to scientific realism is to be found in Laudan 1981.