Refereed articles are peer-reviewed articles. When you are searching in ACMÂ Digital Library and IEEE, you are more likely to find refereed/peer-reviewed articles in journals (not magazines or conference proceedings). To be absolutely sure if something is refereed, you can use Ulrich's.
Refereed/Peer Reviewed Sources
Use Ulrich's to check if a journal is peer-reviewed/refereed:
If you locate an article using the 
button, select the More Options link for a shortcut to Ulrich's: