Rebecca,
Have you checked out the business databases like Business Source Complete or ProQuest One Business? I have often found more articles when looking for "return on investment" for education or training than in education and other subject specific databases especially if they are published in HR or management journals that wouldn't be indexed in CINAHL or PubMed.
Best,
--Christina
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Christina Chan-Park, PhD, MaPA, MSIS (she/her)
STEM Librarian Coordinator and Research Librarian for Science and Data
Liaison to Aviation Science, Biology, Chemistry/Biochemistry, Environmental Science,
Geology, Mathematics, Physics, Psychology/Neuroscience, Statistical Science
Baylor University, One Bear Place #97146, Waco, TX 76798
254-710-4538, 254-710-3116 (fax),
CY_Chan@baylor.eduhttp://orcid.org/0000-0002-6047-9805------------------------------