@article{10_4153_CMB_1978_039_x,
     author = {Wilker, J. B.},
     title = {Russian {Dolls}},
     journal = {Canadian mathematical bulletin},
     pages = {237--240},
     year = {1978},
     volume = {21},
     number = {2},
     doi = {10.4153/CMB-1978-039-x},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1978-039-x/}
}