  We give a~new proof of the known criteria for the inequality
  \begin{equation*}
  \left(\int_{0}^{\infty}\left(\int_{0}^{t}f\right)^{q}w(t)\,dt\right)^{\frac{1}{q}}
  \leq C
  \left(\int_{0}^{\infty}f^{p}v\right)^{\frac{1}{p}}. \end{equation*} The
innovation is in the elementary nature of the proof and its versatility.
