- http://www.cs.princeton.edu/courses/archive/spr06/cos423/Handouts/EPP%20shortest%20path%20algorithms.pdf
- http://www.slac.stanford.edu/pubs/slacreports/reports04/slac-r-104.pdf
Twitter has open sourced a big graph-processing library:
Rate limiting : https://support.twitter.com/articles/160385