  Consider the first-order linear differential equation with several retarded
arguments $$
x^{\prime}(t)+\sum\limits_{i=1}^{m}p_{i}(t)x(\tau_{i}(t))=0,\;\;\;t\geq t_{0},
$$ where the functions $p_{i},\tau_{i}\in C([t_{0,}\infty),\mathbb{R}^{+}),$
for every $i=1,2,\ldots,m,$ $\tau_{i}(t)\leq t$ \ for $t\geq t_{0}$ and $%
\lim_{t\rightarrow \infty}\tau_{i}(t)=\infty $. The state of the art on the
oscillation of all solutions to these equations are established especially in
the case of non-monotone arguments. Examples illustrating the results are
given.
