Complex homogeneous spaces of semisimple Lie groups of type $D_n$

Let $G$ be a connected Lie group, the simple normal subgroups of which are of the first category or are isomorphic to $\operatorname{SO}(2k+1,2l+1)$. In this paper all connected closed subgroups $U$ in $G$ are enumerated for which there exists a complex structure on the manifold $M=G/U$ which is invariant with respect to $G$, and all such structures on $M$ are given.
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