Here's a candidate:
Scheme 2011 is the latest in a long line of revised reports on Scheme. It aims to incorporate the best elements of both previous standards, R5RS and R6RS, while maintaining a minimal, backwards-compatible core. Here we list the major enhancements that Scheme 2011 has over R5RS Scheme, while also documenting the differences from the more ambitious R6RS standard.
We will update the language as the draft solidifies, and take this advice into account, but it would be inaccurate to describe R6RS as more ambitious.