Oscillation of fourth-order strongly noncanonical differential equations with delay argument

The aim of this paper is to study oscillatory properties of the fourth-order strongly noncanonical equation of the form (r3(t)(r2(t)(r1(t)y′(t))′)′)′+p(t)y(τ(t))=0,\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \bigl(r_{3}(t) \bigl(r_{2}(t) \bigl(r_{1}(t)y'(t) \bigr)' \bigr)' \bigr)'+p(t)y \bigl( \tau (t) \bigr)=0, $$\end{document} where ∫∞1ri(s)ds<∞\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$\int ^{\infty }\frac{1}{r_{i}(s)}\,\mathrm {d}{s}<\infty $\end{document}, i=1,2,3\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$i=1,2,3$\end{document}. Reducing possible classes of the nonoscillatory solutions, new oscillatory criteria are established.