Table 1.

Databases searched and corresponding search strings

Database	Search string used
PubMed	(((((assessment[Title/Abstract] OR criteria[Title/Abstract] OR metrics[Title/Abstract] OR characteristics[Title/Abstract] OR measurement[Title/Abstract] OR evaluation[Title/Abstract] OR “Quality Control”[MeSH] OR “Quality Improvement”[MeSH] OR “standards”[Subheading] OR “Guideline”[Publication Type] OR “Guideline Adherence”[MeSH])) OR quality[Title/Abstract]) OR principles[Title/Abstract])) AND ((“Education, Distance”[MeSH] OR e-learning[Title/Abstract] OR electronic learning[Title/Abstract] OR distance education[Title/Abstract] OR technology-enhanced learning[Title/Abstract] OR tele-learning[Title/Abstract] OR web-based learning[Title/Abstract] OR web-based education[Title/Abstract] OR internet-based learning[Title/Abstract] OR computer based learning[Title/Abstract] OR computer-assisted instruction[Title/Abstract] OR distance learning[Title/Abstract] OR online learning[Title/Abstract] OR ((“Learning”[MeSH] OR “Education, Professional”[MeSH]) AND (“Computer Communication Networks”[MeSH] OR “Computer-Assisted Instruction”[MeSH]))))
ISI/Web of Knowledge	(assessment OR criteria OR metrics OR characteristics OR measurement OR evaluation OR standards OR quality OR principles) [TI] AND (e-learning OR (electronic learning) OR (distance education) OR (technology-enhanced learning) OR tele-learning OR (web-based learning) OR (web-based education) OR (internet-based learning) OR (computer based learning) OR (computer-assisted instruction) OR (distance learning) OR (online learning)) [AB]
EBSCO/Cinahl	(assessment OR criteria OR metrics OR characteristics OR measurement OR evaluation OR standards OR quality OR principles) [AB] AND (e-learning OR (electronic learning) OR (distance education) OR (technology-enhanced learning) OR tele-learning OR (web-based learning) OR (web-based education) OR (internet-based learning) OR (computer based learning) OR (computer-assisted instruction) OR (distance learning) OR (online learning)) [AB]
EBSCO/Psychinfo	(assessment OR criteria OR metrics OR characteristics OR measurement OR evaluation OR standards OR quality OR principles) [AB] AND (e-learning OR (electronic learning) OR (distance education) OR (technology-enhanced learning) OR tele-learning OR (web-based learning) OR (web-based education) OR (internet-based learning) OR (computer based learning) OR (computer-assisted instruction) OR (distance learning) OR (online learning)) [AB]
EBSCO/Eric	(assessment OR criteria OR metrics OR characteristics OR measurement OR evaluation OR standards OR quality OR principles) [AB] AND (e-learning OR (electronic learning) OR (distance education) OR (technology-enhanced learning) OR tele-learning OR (web-based learning) OR (web-based education) OR (internet-based learning) OR (computer based learning) OR (computer-assisted instruction) OR (distance learning) OR (online learning)) [AB]
Google Scholar	All in title: (assessment OR criteria OR metrics OR characteristics OR measurement OR evaluation OR standards OR quality OR principles) AND ((e-learning OR (electronic AND learning) OR (distance AND education) OR (technology-enhanced AND learning) OR tele-learning OR (web-based AND learning) OR (web-based AND education) OR (internet-based AND learning) OR (computer AND based AND learning) OR (computer-assisted AND instruction) OR (distance AND learning) OR (online AND learning))