(1).Boxman, Ed A. W. , Paul M. De Graaf and Hendrik D. Flap. 1991. The Impact of Social and Human Capital on the Income Attainment of Dutch Managers. Social Networks 13: 51- 73.
(2).De Graaf Nan Dirk, and Hendrik Derk Flap. 1988. With a Little Help from My Friends: Social Resources as an Explanation of Occupational Status and Income in West Germany, the Netherlands, and the United States. Social Forces 67: 452- 72
(3).Flap, Henk, Beate Volker. 2001. Goal Specific Social Capital and Job Satisfaction Effects of Different Types of Networks on Instrumental and Social Aspectsof Work. Social Networks 23: 297- 320