theorem :: BVFUNC14:18

for Y being non empty set
for G being Subset of (PARTITIONS Y)
for A, B, C, D being a_partition of Y
for z, u being Element of Y
for h being Function st G is independent & G = {A,B,C,D} & A <> B & A <> C & A <> D & B <> C & B <> D & C <> D holds
EqClass (u,((B '/\' C) '/\' D)) meets EqClass (z,A)