CEVAP:

Decision-making as an Approach to the Study of International Politics by Richard C. Snyder, H.W. Bruck, and Burton Sapin (1954: also see Snyder et al., 1963; reprinted in 2002): Contributed a focus on the decision-making process itself as part of the explanation, rather than just foreign policy outputs.

‘Pre-theories and Theories of Foreign Policy’ by James N. Rosenau (a book chapter written in 1964 and published in Farrell, 1966):  Development of actor-specific theory that would lead to the development of generalizable proposition at the level of middle range theory.

Man-Milieu Relationship Hypotheses in the Context of International Politics by Harold and Margaret Sprout (1956: expanded and revised in article form in 1957 and their 1965 book The Ecological Perspective on Human Affairs with Special Reference to International Politics): Foreign policy can only be explained with reference to the psycho-milieu (the psychological, situational, political, and social contexts) of the individuals involved in the decision-making” (Hudson, 2008, p. 14).