\input zb-basic
\input zb-ioport
\iteman{io-port 70211495}
\itemau{Choffrut, Christian; Duboc, Christine}
\itemti{A star-height problem in free monoids with partial communications}
\itemso{ICALP, 190-201 (1987).}
\itemcc{}
\itemut{}
\itemli{doi:10.1007/3-540-18088-5\_15}
\end