Nowakowski,RJ;Landman,BM;Luca,F;University of Witwatersrand, School of Mathematics, Jan Smuts Avenue, Johannesburg,1;Nathanson,MB;Lehman College (CUNY), Department of Mathematics, 250 Bedford Park Boulevard West, Bronx, NY;Nesetril,J;Charles University, Computer Science Institute (IUUK), Malostranske nam 25, Praha;Robertson,A;Colgate University, Department of Mathematics, 219 McGregory Hall, Hamilton, NY