@article{Qian1998,
author = {Qian, Z.},
title= {Changes in Assortative Mating. The Impact of Age and Education, 1970, 1990},
year = {1998},
doi = {10.2307/3004036},
journal = {Demography},
volume = {35},
number = {3},
pages = {279--292},
}