Comment on “Painlevé integrability of two sets of nonlinear evolution equations with nonlinear dispersions” [Phys.†Lett.†A 262 (1999) 344]

In the Letter [1], Lou and Wu studied the Rosenau-Hyman equation and presented various integrable cases. However, some of their results are not correct, due to missing leading order behaviors in the Painlevé test, or to the vanishing of a denominator in the application of the hodograph transformations. Moreover, an integrable case is missing in [1]. In this Comment, we summarize the results of [1] and point out the mistakes and incompletions. For a better understanding, we briefly outline the Painelvé analysis and the application of the hodograph transformations.