— Let p and q be two conjugate exponents (1≤p≤+∞). If fχ−1/q∈L1(G,β) and g∈Lp(G,β), then f and g are convolvable, f∗g is equal locally β-almost everywhere to a function in Lp(G,β), and
∥f∗g∥p≤∥fχ−1/q∥1∥g∥p.
If f∈Lp(G,β) and gχ′−1/q∈L1(G,β), then f and g are convolvable, f∗g is equal locally β-almost everywhere to a function in Lp(G,β), and
∥f∗g∥p≤∥f∥p∥gχ′−1/q∥1.
This follows from Props. 5 and 6 of No. 2 and the remarks in No. 4.
Bourbaki puts the proof directly after the statement, so what is above is the statement and its proof together.