Shawn Garbett provided the following credits in GRATR:
Many thanks to Robert Feldt which also worked on a graph library (http://rockit.sf.net/subprojects/graphr) who pointed me to BGL and many other graph resources. Manuel Simoni found a subtle bug in a preliminary version announced at http://rubygarden.com/ruby?RubyAlgorithmPackage/Graph.
Robert kindly allowed to integrate his work on graphr, which I did not yet succeed. Especially his work to output graphs for GraphViz[http://www.research.att.com/sw/tools/graphviz/download.html] is much more elaborated than the minimal support in dot.rb.
Jeremy Siek one of the authors of the nice book "The Boost Graph Library (BGL)" (http://www.boost.org/libs/graph/doc) kindly allowed to use the BGL documentation as a cheap reference for GRATR. He and Robert also gave feedback and many ideas for GRATR.
Dave Thomas for RDoc[http://rdoc.sourceforge.net] which generated what you read and Matz for Ruby. Dave included in the latest version of RDoc (alpha9) the module dot/dot.rb which I use instead of Roberts module to visualize graphs (see gratr/dot.rb).
Horst Duchene for RGL which provided the basis for this library and his vision.
Rick Bradley who reworked the library and added many graph theoretic constructs.