Comment on `Propagation of solitary waves and shock wavelength in the pair plasma (J. Plasma Phys. 78, 525-529, 2012)'

In a recent paper `Propagation of solitary waves and shock wavelength in the pair plasma (J. Plasma Phys. 78, 525-529, 2012)', Malekolkalami and Mohammadi investigate nonlinear electrostatic solitary waves in a plasma comprising adiabatic electrons and positrons, and a stationary ion background. The paper contains two parts: First, the solitary wave properties are discussed through a pseudopotential approach, and then the influence of a small dissipation is intuitively sketched without theoretical underpinning. Small dissipation is claimed to lead to a shock wave whose wavelength is determined by linear oscillator analysis. Unfortunately, there are errors and inconsistencies in both the parts, and their combination is incoherent.