I take issue with Flora BERNE's use of the phrase, "...professional art dealers such as Christies or Sotheby?s". These are auction houses and not art dealers. True, they sell art works, but are not nearly as well versed as "art dealers". I have often been asked (as an art dealer) for an opinion by some auction houses as to the authenticity of a work of art. These are commercial houses established strictly for the selling of secondary market works of art. I would suggest to Flora BERNE that if she wants "expert" advise, she seek out a reputable art dealer and leave the auction houses to selling other people's rugs, furniture, and art works.
As to the wording one can use for purchasing or selling a work of art, I would suggest the addition of a phrase such as "... free of any liens or encumbrances" to the "warranty"