@article{Litwak1969,
author = {Litwak, E. and Szelenyi, I. },
title= {Primary group structures and their functions: Kin, neighbours, and friends},
year = {1969},
doi = {10.2307/2091957},
journal = {American Sociological Review },
volume = {34},
number = {4},
pages = {465−481},
}