theorem Th15: :: QC_LANG2:15

for A being QC-alphabet
for p1, p2 being Element of QC-WFF A
for x1, x2, y1, y2 being bound_QC-variable of A st All (x1,y1,p1) = All (x2,y2,p2) holds
( x1 = x2 & y1 = y2 & p1 = p2 )