00351nam a2200121Ia 4500082001900000100002000019245004900039260004800088300002200136490006100158500000500219700000500224  a511.5bW461.CK  aWelsh, D. J. A.  aComplexity; knots, colourings and countingb  aCambridgebCambridge University Pressc1993  aviii, 103p. Index  aLondon Mathematical society lecture note seriesv v. 186  a  a