@article{JRAM_1979__306_152091,
     author = {T.Y. Lam and R. Elman and A.R. Wadsworth},
     title = {Orderings under field extensions.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {7--27},
     publisher = {mathdoc},
     volume = {306},
     year = {1979},
     zbl = {0398.12019},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1979__306_152091/}
}