Grammar of Interlingua - A grammar of Interlingua written by Alexander Gode and Hugh Blair. - http://members.optus.net/~ado_hall/interlingua/gi/home/entry_page.html
Interlingua - A description of Interlingua, including vocabulary, grammar, community and sample phrases. - http://en.wikipedia.org/wiki/Interlingua
Alyssa St. James in Interlingua - Facts about Interlingua; a short grammar; tips for learning Interlingua; list of links. Also inside: a short bibliography; a history of Interlingua; and information in Spanish. - http://interlingua.htmlplanet.com/