@article{GDZPPN00220858X,
title = {Extensions of symplectic groupoids and quantization.},
journal = {Journal f\"ur die reine und angewandte Mathematik},
volume = {416},
year = {1991},
pages = {159-190},
zbl = {0722.58021},
url = {http://dml.mathdoc.fr/item/GDZPPN00220858X}
}
Weinstein, Alan; Xu, Ping. Extensions of symplectic groupoids and quantization.. Journal für die reine und angewandte Mathematik, Tome 416 (1991) pp. 159-190. http://gdmltest.u-ga.fr/item/GDZPPN00220858X/