@article{MM2_1991__70_1_155573,
     author = {H. Lange and Ch. Birkenhake},
     title = {Symmetric {Theta-Structures.}},
     journal = {Manuscripta mathematica},
     pages = {67--92},
     publisher = {mathdoc},
     volume = {70},
     number = {1},
     year = {1991},
     zbl = {0737.14013},
     url = {http://geodesic.mathdoc.fr/item/MM2_1991__70_1_155573/}
}