Documents at the pictures

[Ромарио]

Good afternoon. Immediately ask for forgiveness for the banal question, but for beginners they are forgivable. The fact that a strange way (I will not describe) in my life included two pictures, rather well-known masters. Not being a lover of painting, I naturally thought about the implementation of the paintings. And, naturally, there was a lot of questions about the origin of the paintings. I do not know their history and, of course, there are no documents. That's actually we come to the central question: what documents should be in the picture for sale? how to check the history of these paintings (they are not stolen)? Well, how do I justify these pictures?
The question of the Expertise I have worked, of course, in the event of a sale, I will spend it. But it's very do not want to fly into stolen paintings and even more so to miss them ....
Once again I apologize for commercialism, but ....
In general, please write, their knowledge and opinions on this issue ...