theorem :: YELLOW_0:66
for L being non empty transitive RelStr
for S being non empty full SubRelStr of L
for x, y being Element of S st ex_sup_of {x,y},L & "\/" ({x,y},L) in the carrier of S holds
( ex_sup_of {x,y},S & "\/" ({x,y},S) = "\/" ({x,y},L) ) by Th64;