for X being non empty set
for S being SigmaField of X
for M being sigma_Measure of S
for f, g being PartFunc of X,REAL
for m, n being positive Real st (1 / m) + (1 / n) = 1 & f in Lp_Functions (M,m) & g in Lp_Functions (M,n) holds
( f (#) g in L1_Functions M & f (#) g is_integrable_on M )