@techreport{Vaupel1987,
author = {Vaupel, J.W. and Gambill, B.A. and A.I., Yashin},
title= {Thousands of data at a glance: Shaded contour maps of demographic surfaces},
year = {1987},
publisher = {IIASA},
address = {Laxenburg},
institution = {IIASA Research Report RR-87-016},
}