Gretchen L. Matthews The Weierstrass Semigroup of an m-tuple of Collinear Points on a Hermitian Curve. 12-24 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2948&spage=12 2003 conf/fq/2003 International Conference on Finite Fields and Applications db/conf/fq/fq2003.html#Matthews03