Here is the original (?) RIFFMCI.RTF which is a joint specification for storing multimedia data by Microsoft and IBM.

I decided to upload this file here because it is somewhat rare piece of documentation though some parts of it are available on Internet. This copy is mostly ment to help the developers who read HA to gain access to this specification.

This piece of documentation is probably copyrighted by Microsoft and IBM but this is a piece of public documentation distributing which shouldn't be a problem. If a copyright holder wants to have this file removed, I promise to delete this file personally.