A source being scholarly does not always mean it is perfect, or perfect for your research paper.

Here are some questions to ask yourself when evaluating research material:

• Who is the author and what is their affiliation?
• Where is the material published? Is there an editorial board?
• When was it published?
• How did the author gather their data? Is it quantitative or qualitative?
• What other sources are cited?

Let's say you conducted a keyword search and found sources that look good for your research topic. Using the publication evaluation metric, you can also unpack information about the intended audience. Consider this scenario:

• one article is published by the journal Visual Communications
• one article is published by the journal Clinical and Experimental Ophthalmology

First, it can be helpful to use Google (yes!) to find information about your sources. For instance, Google search shows that Visual Communications publishes in the discipline of "theory, research, practical criticism, and creative work in all areas of visual communication," while Clinical and Experimental Ophthalmology publishes "all aspects of clinical practice and research." 

Therefore, the audience for one journal is visual artists, and for the other clinical ophthalmologists.

Unless it is on purpose, including two sources from extremely different areas of study could weaken your argument and/or make writing your paper difficult.