Normal factorization in SL ( 2 , ℤ ) and the confluence of singular fibers in elliptic fibrations. Cadavid, Carlos A.; Vélez, Juan D. — 2009 Beiträge zur Algebra und Geometrie
Towards a new interpretation of Milnor's number. Cadavid, Carlos A.; Vélez, Juan D. — 2008 Revista Colombiana de Matemáticas