Towards an ontology of software maintenance. - Barbara A. Kitchenham; Guilherme Horta Travassos; Anneliese von Mayrhauser; Frank Niessink; Norman F. Schneidewind; Janice Singer; Shingo Takada 001; Risto Vehvilainen; Hongji Yang (J. Softw. Maintenance Res. Pract., 1999)

What Is Preventive Software Maintenance? - Risto Vehvilainen (ICSM, 2000)