Britannica School & Escolar: http://school.eb.com
Britannica E-Stax: http://ebooks.eb.com/texas
Gale/Cengage: http://www.galepages.com/j236901
EBSCO eBooks: http://search.ebscohost.com
ProQuest SIRS Discoverer: http://discoverer.sirs.com
TeachingBooks.net : http://teachingbooks.net/texas