@article{10_4153_CMB_1989_039_x,
     author = {Lambek, J.},
     title = {Grammar as {Mathematics}},
     journal = {Canadian mathematical bulletin},
     pages = {257--273},
     year = {1989},
     volume = {32},
     number = {3},
     doi = {10.4153/CMB-1989-039-x},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1989-039-x/}
}