Over the course of several years, leading to a paper that was presented to the OOPSLA conference in 1995 http://agilix.nl/resources/scrum_OOPSLA_95.pdf
The first Scrum "Framework" book was probably "Agile Software Development with Scrum" by Ken Schwaber and Mike Beedle in 2001. This addressed how Scrum can be used with XP.
The Scrum Framework outlines essential rules and practices for applying Scrum. It sets out to achieve rigor without being unduly prescriptive. The Scrum Process, as originally proposed in OOPSLA 1995, is an earlier work from which the present framework evolved.