@article{Elbers1982,
author = {Elbers, C. and Ridder, G.},
title= {True and spurious Duration Dependence: The Identifiability of Proportitional Hazard Model},
year = {1982},
doi = {10.2307/2297364},
journal = {Review of Economic Studies},
volume = {49},
number = {3},
pages = {403--409},
}