Indoles. XI. Syntheses and stereochemistry of 5,6,7,8,13,13b-hexahydrobenz[a]indolo[2,3-h]quinolizines and of 5,6,7,8,13,13b-hexahydro-14H-bis-indolo[3,2-a][2,3-h]quinolizine. - Lehmann,J.; Nieger,M.; Witt,T. (Heterocycles, 1994)