http://www.skybooksusa.com/time-travel/physics/worengin.htm
http://prola.aps.org/abstract/PRD/v37/i4/p904_1
http://www.citebase.org/abstract?identifier=oai%3AarXiv.org%3A0704.1224&action=citeshits&citeshits=cocitedby
http://www.citebase.org/search?type=identifier&submitted=Co-cited+With&rank=cocitedness&identifier=oai%3AarXiv.org%3A0704.1224
http://scholar.google.ca/scholar?q=gravity+wormhole&hl=en&lr=
http://scholar.google.ca/scholar?hl=en&lr=&q=gravitational+wormhole
http://books.google.com/books?q=gravity+wormhole
http://books.google.com/books?q=gravitational+wormhole
http://www.google.ca/search?hl=en&q=gravity+wormhole&meta=
http://www.google.ca/search?hl=en&pwst=1&q=gravitational+wormhole&start=10&sa=N