1. For a detailed account of the semantic differential, see Charles E. Osgood, George J. Suci, and Percy H. Tannenbaum, The Measurement of Meaning (Urbana, 1957).
2. The Thurstone diagonal method is explained in Osgood, Suci, and Tannenbaum, pp. 332–335. A standard treatment of methods of factor analysis in general is Harry H. Harman, Modern Factor Analysis (Chicago, 1960).
3. Further Experiments in Phonetic Symbolism