A. Escassut, K. Boussaf & J. Ojeda. (1970). Complex and $p$-Adic Meromorphic Functions $f'P'(f)$, $g'P'(g)$ Sharing a Small Function.
            <i>Analysis in Theory and Applications</i>. <i>30</i> (1).
            51-81.
         doi:10.4208/ata.2014.v30.n1.4