@article{03762150, title = {Short proofs of theorems of Lekkerkerker and Ballieu.}, journal = {International Journal of Mathematics and Mathematical Sciences}, volume = {5}, year = {1982}, pages = {609-612}, doi = {10.1155/S0161171282000581}, zbl = {0485.10023}, language = {en}, url = {http://dml.mathdoc.fr/item/03762150} }
Riederle, Max. Short proofs of theorems of Lekkerkerker and Ballieu.. International Journal of Mathematics and Mathematical Sciences, Tome 5 (1982) pp. 609-612. doi : 10.1155/S0161171282000581. http://gdmltest.u-ga.fr/item/03762150/