“…Γ p,w is an interpolation space between L 1 and L ∞ yielded by the Lions-Peetre K-method [4,17]. Obviously Γ p,w ⊂ Λ p,w , and it is wellknown that they coincide as sets with equivalent (quasi) norms if and only if the Hardy operator H 1 is bounded on Λ p,w , which is equivalent to the so-called condition B p , an integral condition satisfied by the weight w [1,27,30]. In particular, the Hardy operator is bounded on L q,p := Λ p,w with w(t) = t p/q−1 , 1 < p, q < ∞ [12], and in that case Λ p,w = Γ p,w as sets with equivalent (quasi) norms.…”