R-Calculus: a Logical Approach for Knowledge Base Maintenance. - Wei Li 022; Ningchuan Shen; Ju Wang (Int. J. Artif. Intell. Tools, 1995)

R-calculus for ELP: An operational approach to knowledge base maintenance. - Ningchuan Shen; Wei Li 022 (J. Comput. Sci. Technol., 1997)