How does copyright work when there are more than one copyright holders?

I am working on a project that will make use a series of educational videos shot in the '80's. While reviewing one of the videos I came across a copyright notice that lists two copyright holders. It says something like "Copyright 1981 and ". What's interesting is that, in this case, is the local School District and is the author of the videos (the person in-camera). This person passed away a few years ago. His estate claims that they hold the rights to the material and, in fact, have been selling the material in video form for years.

I am interested in either partnering with the estate or flat-out acquiring the rights to the material. However, after seeing that notice I became concerned that they might not be in full control of this material (and possibly don't know it). The videos don't sell very well any more so I could not see the School District getting worked-up about them. However, my plan is to bring them current and re-market them to an entirely new crowd and, obviously to sell a lot more units per month.

I just pinged them with a request for clarification and will probably consult with an IP attorney if the deal gets serious. Just looking for comments and opinions about this kind of a situation. Does "and" in a copyright notice mean that you have to negotiate with both parties or is it enough to negotiate with one of them?

The very first thing you need to do is contact the people selling the videos and ask them for proof that the School District has assigned all rights to what is now their estate.

If they can not provide you with proof, you will have to negotiate with both parties. (Good luck) If they can provide you with a copy of that assignment, you just have to deal with the estate.

You'll have to negotiate with both parties.
http://www.copyright.com/Services/copyrightoncampus/compliance/index.html