Asymptotic behavior of CLS estimators for $2$-type doubly symmetric   critical Galton-Watson processes with immigration
  In this paper, the asymptotic behavior of the conditional least squares (CLS) estimators of the offspring means $(\alpha,\beta)$ and of the criticality parameter $\varrho:=\alpha+\beta$ for a $2$-type critical doubly symmetric positively regular Galton-Watson branching process with immigration is described. 
M\'arton Isp\'any, Krist\'of K\"ormendi, Gyula Pap
math.PR