I would like to present to you the work of a guy named Jan Pająk. He is a professor, but most think he is crazy. below there is a link to his theories. he writes about UFOnauts( this is how he calls aliens) and their agenda. Some of his views are similar to those of other researchers in the field of ufology, and some are totally new. The material is very long but you can always click on what interests you at the moment. The material is in all major languages and you can choose the version that is best for you to read by clicking on the left side.
http://www.totalizm.pl/pajak_jan_uk.htm