Incidence matrix
9 | 2 2 4 | 1 6 6 4 | 2 5 4
--+--------+-----------+------
2 | 9 * * | 1 2 0 2 | 2 2 1 ab x
2 | * 9 * | 0 0 2 2 | 1 2 1 ad x
2 | * * 18 | 0 2 2 0 | 0 2 2 ae q
--+--------+-----------+------
3 | 3 0 0 | 3 * * * | 2 0 0 abc xxx verf(tet)
3 | 1 0 2 | * 18 * * | 0 1 1 abf xqq verf(trip)
3 | 0 1 2 | * * 18 * | 0 1 1 adg xqq verf(trip)
4 | 2 2 0 | * * * 9 | 1 1 0 abed xxxx verf(oct)
--+--------+-----------+------
6 | 6 3 0 | 2 0 0 3 | 3 * * abcdef verf(rap)
5 | 2 2 4 | 0 2 2 1 | * 9 * abdei verf(ope)
4 | 1 1 4 | 0 2 2 0 | * * 9 abfi verf(triddip)
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