@article{Schumacher1987,
author = {Schumacher, M. and Olschewski, M. and Schmoor, C.},
title= {The impact of heterogeneity on the comparison of survival times},
year = {1987},
doi = {10.1002/sim.4780060708},
journal = {Statistics in Medicine},
volume = {6},
number = {7},
pages = {773--784},
}