How do I get a picture authenticated?

Hi
A family friend, now an elderly lady was once a personal friend of Pablo Picasso. He gave her a picture which she subsequently gave to me some 27 years ago. My efforts to obtain any authentication have been fruitless. Sothebys, Christies, Bonhams etc all dismiss it out of hand as being of no value. The picture is so obviously in the style of Picasso, but is not shown in any of the official listings.I'm told it may be a lithograph, but if so, why are there no more and why can I feel paint on the surface of the paper. So many questions, but no answers! Can anyone help please? (When I can, I will attach a photograph)

Hi
I will ask around and see if anyone has any Ideas for you.
Did you try to find Professors of fine art that specialize in Picasso?
I am sure that if you are going to get any help on the internet you are going to need to photograph and post the picture...

Thanks Heather.
I've posted a photo of the painting in the general community photographs. I'm not sure if this is the right place as I'm still trying to find my way around the site!! If I need to put it somewhere else for you (and others) to see, please let me know where.... and how!
Many thanks

Peter