Irwin, L., L.(1980).Discovering whether programs work : a guide to statistical methods for program evaluation / Laura Irwin Langbein (Cet.1).:Goodyear Publishing Company.
Gaya MLA
Langbein, Laura, Irwin."Discovering whether programs work : a guide to statistical methods for program evaluation / Laura Irwin Langbein".Cet.1:Goodyear Publishing Company,1980.Textbook.