Friendship
Concept
Birds of a Feather: Homophily in Social Networks
2001 · Miller McPherson, Lynn Smith‐Lovin, et al. · Annual Review of Sociology
The Benefits of Frequent Positive Affect: Does Happiness Lead to Success?
2005 · Sonja Lyubomirsky, Laura King, et al. · Psychological Bulletin
Intergroup Contact Theory
1998 · Thomas F. Pettigrew · Annual Review of Psychology