Two common ways to find scholarly journal articles:
1. Search an article database and then limit the search to scholarly (peer-reviewed or refereed) materials; or
2. Locate a journal and verify if it is a scholarly one, using Ulrich's Global Serials Directory database.
If you are still unsure of whether a journal is a scholarly journal or not, the best source to turn to is an expert in your field -- ask your professor.
1) At a subject database (such as SciTech Premium Complete)
2) Enter a keyword at the search box and select Peer reviewed option (if available)
3. Then select Scholarly Journals to limit the results
1) Open Ulrich's Global Serials Directory database
2) Click on Advanced Search link
3) Enter keywords at the search box (such as engineering)
4) Limit your results > Content Type: check "Academic/Scholarly" box
This way you will find a set of academic/scholarly journals in the field of marketing.