@article{Klein Ikkink1999,
author = {Klein Ikkink, K. and Van Tilburg, T.},
title= {Broken ties: Reciprocity and other factors affecting the termination of older adults' relationships},
year = {1999},
doi = {10.1016/S0378-8733(99)00005-2},
journal = {Social networks},
volume = {21},
number = {2},
pages = {131--146},
}