\input zb-basic
\input zb-ioport
\iteman{io-port 70314649}
\itemau{Charlton, David; Demaine, Erik D.; Demaine, Martin L.; Dujmovic, Vida; Morin, Pat; Uehara, Ryuhei}
\itemti{Ghost chimneys}
\itemso{CCCG, 63-66 (2010).}
\itemcc{}
\itemut{}
\itemli{http://cccg.ca/proceedings/2010/paper19.pdf}
\end