This is a port of the weight-balanced tree library used by MIT Scheme to CHICKEN 5 Scheme.
The R4RS version of this library is the work of Stephen Adams and was, I think, adapted from the MIT Scheme version, also by Adams. Peter Lane made some R7RS adaptations in 2017.
This version of the library was adapted for CHICKEN by Wolfgang Corcoran-Mathe.
GPL version 2.