00265nam a2200097Ia 4500008004100000082001600041100002200057245004400079264003400123300001000157200527s9999||||xx |||||||||||||| ||und||  a150.287 HEL  aHelmstadter, G.C. 0aPrinciples of Psychological Measurement  bAppleton-Century Croftsc1964  a248p.