The main objective of this article is to improve and complement some of the oscillation criteria published recently in the literature for third order differential equation of the form (r(t)(z″(t))α)′+q(t)f(x(σ(t)))=0,t≥t0>0,\\documentclass[12pt]{minimal}\t\t\t\t\\usepackage{amsmath}\t\t\t\t\\usepackage{wasysym}\t\t\t\t\\usepackage{amsfonts}\t\t\t\t\\usepackage{amssymb}\t\t\t\t\\usepackage{amsbsy}\t\t\t\t\\usepackage{mathrsfs}\t\t\t\t\\usepackage{upgreek}\t\t\t\t\\setlength{\\oddsidemargin}{-69pt}\t\t\t\t\\begin{document}$$ \\bigl( r(t) \\bigl( z^{\\prime \\prime }(t) \\bigr) ^{\\alpha } \\bigr) ^{\\prime }+q(t)f \\bigl(x \\bigl(\\sigma (t) \\bigr) \\bigr)=0,\\quad t\\geq t_{0}>0, $$\\end{document} where z(t)=x(t)+p(t)x(tau (t)) and α is a ratio of odd positive integers in the two cases int _{t_{0}}^{infty }r^{frac{-1}{alpha } }(s),mathrm {d}s<infty and int _{t_{0}}^{infty }r^{frac{-1}{alpha } }(s),mathrm {d}s=infty . Some illustrative examples are presented.