TY - CHAP A1 - Vaupel, J.W. A1 - Yashin, A. I. T1 - Unobserved Population Heterogeneity Y1 - 2006 A3 - Caselli, G. A3 - Vallin, J. A3 - Wunsch, G. T2 - Demography: analysis and synthesis; a treatise in population studies, volume 1 CY - London PB - Academic Press SP - 271 EP - -278 ER -