“…Rubio de Francia in 1984, see [14], roughly speaking, if an operator preserves L p 0 (w) for all w ∈ A p 0 , then it necessarily preserves the L p (w) space for every w ∈ A p , and every 1 < p < ∞. Extensions of this result were obtained by several authors, for instance in [5] and [6], E. Harboure, R.A. Macías and C. Segovia study A(p, q) classes, pairs of weights and extreme cases, p 0 = ∞; more recently F. Martín-Reyes, P. Ortega and A. de la Torre, see [9], considered this problem for one-sided classes of weights for 1 ≤ p 0 < ∞. (The one-sided classes of weights were first introduced by Sawyer in [13].)…”