\input zb-basic
\input zb-ioport
\iteman{io-port 03720939}
\itemau{Hall, Dick Wick}
\itemti{Rochromials and the colourings of circuits.}
\itemso{Graph theory and related topics, Proc. Conf. Honour W. T. Tutte, Waterloo/Ont. 1977, 233-245 (1979).}
\itemcc{}
\itemut{constrained chromial; free chromial}
\itemli{}
\end