Three daunting facts confront anyone interested in buying one of Amedeo Modigliani’s distinctive elongated portraits. They tend to have multimillion price tags; they are a favorite of forgers; and despite an abundance of experts, no inventory of his works is considered both trustworthy and complete.

Christian Parisot, for instance, the author of one catalog and the president of the Modigliani Institute in Rome, is due in court this week in Rome on charges that he knowingly authenticated fake works.

Marc Restellini, a French scholar compiling another survey of Modigliani’s work, jettisoned part of his project years ago after receiving death threats.

And even those who swear by a listing of 337 works created by the appraiser and critic Ambrogio Ceroni acknowledge it has significant gaps. The effort to establish an authoritative record of Modigliani’s work “resembles nothing so much as a soap opera,” Peter Kraus, an antiquarian book dealer, wrote in an essay published a decade ago.