Trade sources are also known as industry magazines (e.g., AdWeek, Publisher's Weekly, Forbes, etc.).
Click this link and take a few minutes to bowse this PG Library trade article. Pay attention to the information on the detailed record page, including Author, Source, and Abstract, as well as the HTML link on the left side of the screen
Things to consider:
After browsing this item, can we trust that it passes the criteria as a credible trade publication? If answering yes, then chances are it is a source of credible information. If answering no, then you may want to consider an alternate source.