Source: Smokerz Paradise
In addition to the resources below, more information is available from the U.S. Government. Try a search at USA.gov, the government's official web portal.
Thanks to the following for sharing portions of their LibGuides:
The University of Rhode Island: http://uri.libguides.com/ecigs
University of Illinois at Urbana-Champaign: http://guides.library.illinois.edu/electroniccigarettes