@inbook{Morgenstern1998,
author = {Morgenstern, H.},
title= {Ecological studies},
year = {1998},
editor = {Rothman, K.J.},
editor = {Greenland, S. },
booktitle = {Modern Epidemiology},
address = {Philadelphia, PA},
publisher = {Lippincott-Raven},
pages = {459--480},
}