. . . "educational materials" . "open educational resource" . "free resources" . "open copyright" . "Open Educational Resources" . "resources" . . . "open educational resources" . . "OERs" . . . . . . . "Open Education" . "open educational resources (OER)" . "OER initiatives" . "Open Educational Resource" . . "textbook trading" . "Open educational resources" . . . . . "open education resources" . . . . "open sharing of educational resources" . "educational resources" . . "Open educational resources" . "open educational applications" . . . "OER" .