A comprehensive study of small, clustered O-linked glycopeptides in this area comes from Live, et al., who determined the 3-dimensional structures of several (penta)-glycopeptides with a contiguous Ser-Thr-Thr motif glycosylated with either the tumor-associated antigens Tn (GalNAc), TF (Gal-β1,3-GalNAc) or 2,6-sialyl TF (Gal-β1,3-(α-2,6-Neu5Ac)GalNAc) glycosylation. Here, GAL is linked to neoplasm.