Are think tanks unbiased sources of information? It depends. See...
Carefully evaluate all information, whether from a book, article, or website, by asking the following questions:
MLA Handbook. 8th ed., The Modern Language Association, 2016, pp. 11-12.
MLA also provides a great checklist for evaluating sources.
Searching for information about the author or organization responsible for the website, article, or book is an excellent way of evaluating sources. This method is called lateral reading.
Please watch "Sort Fact from Fiction Online with Lateral Reading" produced by the Civic Online Reasoning Institute at Stanford University. The video is under four minutes. The University of Louisville Libraries also has this useful handout about lateral reading.