References Blomster, Jeffrey P. ; Hector Neff , and Michael D. Glascock (2005-02-18). "Olmec Pottery Production and Export in Ancient Mexico Determined Through Elemental Analysis". Science (Washington, DC: American Association for the Advancement of Science ) 307 (5712): pp.1068–1072. doi : 10.1126/science.1107599 . ISSN   0036-8075 . OCLC   204603069 .