\input zb-basic
\input zb-ioport
\iteman{io-port 00898021}
\itemau{Farley, Jonathan David}
\itemti{The number of order-preserving maps between fences and crowns.}
\itemso{Order 12, No.1, 5-44 (1995).}
\itemab
The paper deals with enumeration of order-preserving and -reversing maps between special poset classes, like fences and crowns. It starts with an extensive historical account on the topic and then supplies exact formulae. The proofs operate with lengthy but elementary calculations.
\itemrv{P.L.Erd\"os (Budapest)}
\itemcc{}
\itemut{order-preserving maps; order-reversing maps; Pascal's triangle; fences; crowns}
\itemli{doi:10.1007/BF01108588}
\end