@article{SF_1993__47_2_135254,
     author = {P.E.T. Jorgensen and X.C. Quan},
     title = {Positivity and cohomology for involutive semigroups.},
     journal = {Semigroup forum},
     pages = {60--80},
     publisher = {mathdoc},
     volume = {47},
     number = {2},
     year = {1993},
     zbl = {0818.46067},
     url = {http://geodesic.mathdoc.fr/item/SF_1993__47_2_135254/}
}