<font color="#ff8000">Given the isomorphisms stated above, the order of the sandpile group is the determinant of {\displaystyle \Delta '}\Delta ', which by the matrix tree theorem is the number of spanning trees of the graph.</font> | <font color="#ff8000">Given the isomorphisms stated above, the order of the sandpile group is the determinant of {\displaystyle \Delta '}\Delta ', which by the matrix tree theorem is the number of spanning trees of the graph.</font> |