These links will take you to information from sources I consider very useful to developing a basic understanding of  the topic of extraterrestrial contact.  

https://www.youtube.com/watch?v=tGMGOdKOPKk

https://www.youtube.com/watch?v=UWCMPyLSlSo

https://www.youtube.com/watch?v=BtmpaM0PqyI