The fake lithographs by Dali - Picasso - Chagall etc

Most important articles by specialist in lithographs:

Lee Catterall: The great Dali fraud...read
there are many chapters and pages about the question don't forget to look at all the pages! Atoning.

Paul Baker:Policing fakes...read
a conference in Sydney Australia about the question. 9 pages of documents.

World Print Makers: How not to be " duped" in the world of the Fine Art Print market...read

Kobi Lendor: A guide to collectiong Picasso prints...read

My conclusion: If you will have read all this, I don't doubt you will be very careful where you buy a lithograph.

For Chagall, Picasso, Miro: there is only one great specialist: Eric Mourlot. his website.
They are printers of lithographs in France since 1852! Eric Mourlot is very friendly man, and speaks fluently English, he has his Gallery in NY. They printed most of the lithographs of the great Modern masters, no doubt that you will have with him "the expert".