@article{10_4153_CJM_1976_095_6,
     author = {Bruns, G\"unter},
     title = {Free {Ortholattices}},
     journal = {Canadian journal of mathematics},
     pages = {977--985},
     year = {1976},
     volume = {28},
     number = {5},
     doi = {10.4153/CJM-1976-095-6},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1976-095-6/}
}