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**Graph problem!!!**

Proove that:

If we have a matrix

|e11 e12 ... e1n|

|e21 e22 ... e2n|

| ..................... |

|en1 en2 ... enn|

(eij edges of a graph G)

where every row is a spanning tree of G

then

there is a recomposition of every row so that the columns are also spanning trees of G.