\input zb-basic
\input zb-ioport
\iteman{io-port 50319728}
\itemau{Shen, Ningchuan; Li, Wei}
\itemti{R-calculus for ELP: an operational approach to knowledge base maintenance}
\itemso{J. Comput. Sci. Technol. 12, No. 1, 17-28 (1997).}
\itemcc{}
\itemut{}
\itemli{doi:10.1007/BF02943141}
\end