Post Correspondence Problem for short words.

Vesa Halava Tero Harju Mika Hirvensalo Juhani Karhumäki Post Correspondence Problem for short words. 115-118 2008 108 Inf. Process. Lett. 3 http://dx.doi.org/10.1016/j.ipl.2008.04.013 db/journals/ipl/ipl108.html#HalavaHHK08