It will be hard to find some credible sources right now especially if you would check online. You will know that the source is credible if it would also place its own sources that will prove that the information that is has presented is correct. You may want to get more information from Quizlet. This will provide you details that are also based on other credible sources.
You will know that a source is credible if the article or the journal can be discussed properly by the author. If there are not enough details about the source or how the source has gotten the information, this might be an indication that the source is not as reliable as you have thought.