\input zb-basic
\input zb-ioport
\iteman{io-port 71038615}
\itemau{Christensen, Helle L.; Haslund, Mads L.; Nielsen, Henrik N.; Tryfona, Nectaria}
\itemti{Operations for conceptual schema manipulation: definitions and semantics}
\itemso{ADBIS, 225-238 (2001).}
\itemcc{}
\itemut{}
\itemli{doi:10.1007/3-540-44803-9\_18}
\end