Hello. You did not submit the article to which this question refers, which makes it impossible for it to be answered. However, I will try to help you in the best possible way.
To answer this question, you will need to read the entire article that Manuel used in the research. If this article presents statements that are supported by evidence and facts, that article is reliable, otherwise the article is not reliable. In addition, this article, in order to be reliable, must present the research sources you used to write. These research sources must have been carried out by people or institutions specialized in the subject addressed.