Scheme is so old that there is not one language but rather a family of dialects that are considered Schemes. The Scheme community has several times made a stand

Scheme is so old that there is not one language but rather a family of dialects that are considered Schemes. The Scheme community has several times made a standard on the parts of the language(s) that various implementors can agree on. The standard is small though. All the major Scheme implementations come with many language constructs and libraries not covered by the standard. Racket started as a Scheme but changed name to Racket a few years ago to signal that the racket language is much more than plain standard Scheme. One remarkable thing about Racket is the that the module system allows implementing other languages as modules with relative ease. Included in the Racket distribution is therefore an implementation of R6RS (and R5RS) the most recent standard (R7RS is coming soon). Also included is implementation is a typed version of Racket, an implementation of a logic programming language and, yes your eyes are not deceiving you, Algol 60.