Reference
González-Díaz, R., Ion, A., Iglesias-Ham, M., & Kropatsch, W. (2009). Irregular Graph Pyramids and Representative Cocycles of Cohomology Generators. In Proceedings of the 7th IAPR-TC15 International Workshop on Graph-based Representations in Pattern Recognition (pp. 263–272). Springer. http://hdl.handle.net/20.500.12708/52920