BERKOWITZ, L. (1954). Group standards, cohesiveness, and productivity . Hum. Relat.7, 509-519 .
2.
BROWN, W. H. (1953). Instrument for studying viscidity within small groups . Educ. psychoL. Measurements13, 402-417 .
3.
FESTINGER, L. , SCHACHTER, S. & BACK, K. (1950). Social pressures in informal groups. New York: Harper & Brothers; London: Tavistock Publications , 1963.
4.
LIBO, L. M. (1953). Measuring group cohesiveness. Ann Arbor, Michigan: Research Center for Group Dynamics, Institute for Social Research, University of Michigan .
5.
ROTTER, J. B. (1954). Social learning and clinicalpsychology. New York: Prentice-Hall .
6.
SCHACHTER, S. et al. (1951). Effects of group cohesiveness upon conformity of individuals to group standards . Hum. Relat.4, 229-238 .
7.
SIEGEL, S. (1956). New parametric statistics for the behavioral sciences. New York: McGraw-Hill .
8.
WORELL, L. (1959). Level of aspiration and academic success . J. educ. Psychol., 50, 47-54 .