@article{SIGMA_2017_13_a12,
     author = {Mauricio A. Escobar Ruiz and Ernest G. Kalnins and Willard Miller Jr. and Eyal Subag},
     title = {B\^ocher and {Abstract} {Contractions} of $2$nd {Order} {Quadratic} {Algebras}},
     journal = {Symmetry, integrability and geometry: methods and applications},
     year = {2017},
     volume = {13},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SIGMA_2017_13_a12/}
}