@article{Seal1945,
author = {Seal, H.L.},
title= {The mathematics of a population composed of k stationary strata each recruited from the stratum below and supported at the lowest level by a uniform annual number of entrants},
year = {1945},
doi = {10.2307/2332300},
journal = {Biometrika},
volume = {33},
number = {3},
pages = {226--230},
}