APA
Knapp Charles L, Crystal Nathan M, . (1987). Problems in contract law : Cases and materials. Boston: Little, Brown & Co.
Chicago
Knapp Charles L, Crystal Nathan M, . 1987. Problems in contract law : Cases and materials. Boston: Little, Brown & Co.
Harvard
Knapp Charles L, Crystal Nathan M, . (1987). Problems in contract law : Cases and materials. Boston: Little, Brown & Co.
MLA
Knapp Charles L, Crystal Nathan M, . Problems in contract law : Cases and materials. Boston: Little, Brown & Co. 1987.