@article{MZ_1990__205_3_174192,
     author = {J\'an Min\'ac and Michel Spira},
     title = {Formally real fields, pythagorean fields, {C-fields} and {W-groups.}},
     journal = {Mathematische Zeitschrift},
     pages = {519--530},
     publisher = {mathdoc},
     volume = {205},
     number = {3},
     year = {1990},
     zbl = {0692.12005},
     url = {http://geodesic.mathdoc.fr/item/MZ_1990__205_3_174192/}
}