For many years, nearly all references about machines as a language for thinking have been specialized and limited. Colleges with scholars who write textbooks usually have not had a variety of expensive and versatile computing machinery. As a result, the main environment for stimulating possible authors has until recently been missing. The list of references is accordingly brief. AIKEN, HOWARD H., and others, _Proceedings of a Symposium on Large-Scale Digital Calculating Machinery_, Cambridge, Mass.: Harvard University Press, 1948, 302 pp. COMRIE, JOHN LESLIE, The Application of Commercial Calculating Machines to Scientific Computing, _Mathematical Tables and Other Aids to Computation_, vol. 2, no. 16, Oct. 1946, pp. 149-159. CREW, E. W., Calculating Machines, _The Engineer_, vol. 172, Dec. 1941, pp. 438-441. FRY, MACON, _Designing Computing Mechanisms_, Cleveland, Ohio: Penton Publishing Co., 1946, 48 pp. (Reprinted from _Machine Design_, Aug. 1945 through Feb. 1946.) HARTREE, D. R., _Calculating Machines: Recent and Prospective Developments and Their Impact on Mathematical Physics_, Cambridge, England: The University Press, 1947, 40 pp. HORSBURGH, E. H., _Modern Instruments and Methods of Calculation_, London: G. Bell and Sons, Ltd., 1914, 343 pp. LILLEY, S., Mathematical Machines, _Nature_, vol. 149, Apr. 25, 1942, pp. 462-465. MURRAY, FRANCIS J., _The Theory of Mathematical Machines_, New York: King’s Crown Press, 1947, 116 pp. The author states that a mathematical machine is a mechanism that provides information concerning the relationships among a specified set of mathematical concepts. TURCK, J. A. V., _The Origin of Modern Calculating Machines_, Chicago: Western Society of Engineers, 1921. Recently, however, some magazine and newspaper publishers have seen news value in machines that think, and some good general articles with appeal to a wide audience have appeared. For the references to these articles, see the section of this supplement entitled “Digital Machines—Miscellaneous.” PUNCH-CARD CALCULATING MACHINES There are a few general references on punch-card calculating machines: BAEHNE, G. WALTER, editor, and others, _Practical Applications of the Punched Card Method in Colleges and Universities_, New York: Columbia University Press, 1935, 442 pp. This is a collection of many contributions from a number of authors, describing various applications, chiefly educational. ECKERT, W. J., _Punched-Card Methods in Scientific Computation_, New York: Columbia University, The Thomas J. Watson Astronomical Computing Bureau, 1940, 136 pp.