Please help with autographs! (Tex Ritter and others....)

Ok, we found this in a bunch of stuff my Mother-in-Law had. Its a music/songbook of Tex Ritter Cowboy songs. It's dated 1941, and is complete with little wear. It appears that he signed it, and there are 2 other autographs. So.....I have a few questions:

1. Can anyone tell who the other signatures are from?

2. How do I go about authenticating something like this? Or is it even worth it?...

3. If these are real, any rough ballpark of what it might be worth??

4. Any online resources that could help me?? Autographs are not my specialty. lol

Thanks in advance for any info!

 

Edward and Edwin Milo were country singers known as the Milo twins.

Also, Tex Ritter was the father of John Ritter (Three's Company)

The sheet music is listed for at least $15 or more, in various states of disrepair.

 

Is that price for signed, or unsigned? Do the autographs give them any more value?

 

The other signature is Slim Andrews, Tex's comic sidekick.
https://www.fandango.com/people/slim-andrews-18307/biography
There is a seller of autographs online that is selling a Slim Andrews autograph for $25.

 

https://www.google.com/search?q=tex...UMLKwKHeUxC9QQ_AUoAnoECAsQBA&biw=1366&bih=657
Lots of examples, but I did not see any that were signed. It seems like the autographs would enhance the value, but perhaps it depends on who the buyer is?

 

Above the Milo twins signatures, it appears there is "PRC" written in ink. That may be a reference to PRC Studios. Tex Ritter starred in movies for that studio.