:The opera does not exist because someone's family member has decided to publish a new edition prepared by someone with the same last name.  The opera has existed before and will exist after this edition has been forgotten. If this family of "Halèvy" experts are notable, you're more than welcome to write articles about them, as long as they can be traced to reliable sources such as "Grove" and the like.  "Self-publishing" does not count here. But expecting these people to have equal billing with the actual composer of the opera simply because somebody has gotten a photocopy of the score from the Paris Opera library is a bit much, I should say...