Jd. Biggins et Jc. Dsouza, THE SUPERCRITICAL GALTON-WATSON PROCESS IN VARYING ENVIRONMENTS - SENETA-HEYDE NORMING, Stochastic processes and their applications, 48(2), 1993, pp. 237-249
A natural sufficient condition is given for a Galton-Watson process in
a varying environment to have a single rate of growth that obtains th
roughout the survival set of the process. In the homogeneous process t
he growth rate is provided by the usual Seneta-Heyde norming.