@incollection{AST_1989__179-180__39_0,
     author = {Carlson, James A. and Hain, Richard M.},
     title = {Extensions of variations of mixed {Hodge} structure},
     booktitle = {Th\'eorie de Hodge - Luminy, Juin 1987},
     editor = {Barlet D. and Esnault H. and Elzein F. and Verdier Jean-Louis and Viehweg E.},
     series = {Ast\'erisque},
     pages = {39--65},
     publisher = {Soci\'et\'e math\'ematique de France},
     number = {179-180},
     year = {1989},
     mrnumber = {1042801},
     zbl = {0717.14004},
     language = {en},
     url = {http://www.numdam.org/item/AST_1989__179-180__39_0/}
}