Always up-to-date: The guidelines of the international library association IFLA for recognizing "fake news".
The following criteria may be helpful by assessing the quality of the results of your literature search.
However, in case of doubt we recommend you to discuss the use of a publication for your thesis with your teacher.
Documents listed in a database are in general of good quality and a critical quality assessment is especially important for documents / information found in the internet.
Purpose of publication
What is the purpose of a publication? Who is the target group of the publication?
Present new research result, scientific conferences vs. advertising, lobbying
Experts, research community vs. customers, the general public
Author / publisher / editor
Do you know the authors name or is the document published anonymously?
Who are the authors? What is their profession? What is their acacemic degree?
What reputation does the publisher / editor have?
Research insitutes, university, authorities, museums vs. companies
Date of publication / update
When was the document published?
When was the web site updated?
References
What kind of literature is referenced in the publication?
Is there a bibliography?
What web sites are referred to?
Peer review
Is the article published in a peer reviewed journal?
Peer review is the evaluation of a publication by one or more people of similar competence to the author and constitutes a form of self-regulation by qualified members of a profession. Peer review methods are employed to maintain standards of quality, improve performance, and provide credibility.
To check if a journal is peer reviewed go to: Ulrichsweb: International Periodicals Directory.
Journal reputation
What reputation has the journal within the scientific community?
There are different indicators for a journal's reputation. One of them is the impact factor (IF) that is a measure reflecting the average number of citations to recent articles published in a journal. Check the IF of a journal via the InCites Journal Citation Report.
URL
The URL can give you an idea of the background of a web site.
uni-, .edu, .org, .gov, .admin vs. .com
Besides the formal quality assessment you also have to find out if a publication is relevant to your research question in terms of content. To gain a first impression of a publications content have a look at the abstract, the preface, the introduction and the table of content.