Papers in Psychology
The series ran from DPP1 to DPP15. Random House took over publication of three series from Doubleday in 1956 (Papers in Psychology, Short Studies in Political Science, and Short Studies in Sociology), rebranding them as Random House series and republishing many of the earlier titles (see Random House Acquires Doubleday's Textbook Dept., 168 PW 1553 (Oct. 1, 1955)).
Titles DPP1 to DPP15 were rebranded PP1 to PP15 and republished in the new Random House Studies in Psychology series.
Frank L. Schick, THE PAPERBOUND BOOK IN AMERICA 215-16 (Bowker 1958) ("In August, 1955, Random House took over the College Textbook Department of Doubleday and incorporated fifty titles which were involved in this transfer into the operations of its own college department. Among the materials acquired were the series of 'Short Studies' in sociology, political science and psychology.")