a. Even subgraphs, cycle space, edge cuts, and cut space

b. Planar duality
c. Boundary subgraphs
d. Z2-homology
e. Systems of cycles and cocycles
f. Homology anotations
g. Dual of minimum cut is minimum-weight Z2-homologous subgraph
h. Z2-homology cover
i. MSSP again: 2^{O(g)} n log n time