@article{Luke2011,
author = {Luke, N. and Clark, S. and Zulu, E.M.},
title= {The relationship history calendar: Improving the scope and quality of data on youth sexual behavior},
year = {2011},
doi = {10.1007/s13524-011-0051-2},
journal = {Demography},
volume = {48},
number = {3},
pages = {1151--1176},
}