[plt-scheme] Smallest set of operators

Hello all,

Due to my current work, I've been lately overwhelmed about Programming
Languages Theory which fascinated me and I read a little bit when I
had the time but lately I do it for research purposes. While reading
some programming language and compiler books I wondered if there is
any known minimal set of Scheme operators from which you can define
the rest of standard.

I could just throw an idea regading this what I think this set should
be but it would probably wrong. Still, since Scheme is so well defined
syntactically and semantically if there has been any theoretical work
on this minimal set of operators.

References would be appreciated.

Regards,

-- 
Paulo Jorge Matos - pocm at soton.ac.uk
http://www.personal.soton.ac.uk/pocm
PhD Student @ ECS
University of Southampton, UK