You should check with the office of the Association of Art Museum Directors
in New York City, attn. Mimi Gaudieri, exec. director.  The association
prepared guidelines on this topic several years ago.  I'm sorry I don't have
the phone number with me here.  Another good source to ask would be the Getty
Museum in L.A.
 
Paul D. Schweizer
Munson-Williams-Proctor Institute
Utica, New York