@article{10_4153_CJM_1991_039_9,
     author = {Colbourn, Charles J. and Rosa, Alexander and Stinson, Douglas R.},
     title = {Pairwise {Balanced} {Designs} with {Block} {Sizes} {Three} and {Four}},
     journal = {Canadian journal of mathematics},
     pages = {673--704},
     year = {1991},
     volume = {43},
     number = {4},
     doi = {10.4153/CJM-1991-039-9},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1991-039-9/}
}