Since you are looking for sources that you can use for your research project, it is actually best for you to use websites that have a url ending in .edu, since you can trust that the source is valid and reliable.
A .html and .com do not mean that the site is trustworthy since even a blog can have a .com url. You might be able to find trustworthy information in a .org site, but you have to research the organization first beforehand.