Why collect retrospective data? /
Butz, William P.,
Why collect retrospective data? / William P. Butz - 12 pages ; 28 cm. - The Rand paper series; P-6715 . - The Rand paper series; P-6715 .
Demographic surveys.
Why collect retrospective data? / William P. Butz - 12 pages ; 28 cm. - The Rand paper series; P-6715 . - The Rand paper series; P-6715 .
Demographic surveys.
