Would Wikipedia count? https://en.wikipedia.org/wiki/Jim_Henson  or https://en.wikipedia.org/wiki/Jim_Henson_Television   There are others also on Wikipedia.  IMDB also has information https://www.imdb.com/name/nm0001345/

I am sure that the Puppetry Journal would count but they are not freely available. https://www.puppeteers.org/journal/index/   You would have to search the index to figure out which issues had articles.  One I know of is https://www.puppeteers.org/puppetry-journal/fall-2005-volume-57-no-1/   They do have a DVD of them from 1949-1980 for sale but of more current ones you might have to see if you can purchase a back issue of it. 

...And with a little bit of research, I answered my own question.   https://en.wikipedia.org/wiki/Wikipedia:Academic_use    It seems that Wikipedia is not considered an scholarly source by many academics .  What you might be able to get from it though are sources that are since they are often listed at the bottom.