@article{10_4064_fm229_3_3,
     author = {Pawe{\l} G{\l}adki and Murray Marshall},
     title = {Quotients of index two and general quotients
 in a space of orderings},
     journal = {Fundamenta Mathematicae},
     pages = {255--275},
     publisher = {mathdoc},
     volume = {229},
     number = {3},
     year = {2015},
     doi = {10.4064/fm229-3-3},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/fm229-3-3/}
}