Q:

Missing var greek letters in math mode using eulervm

The eulervm package lacks the varrho and varsigma greek letters. Can I replace them by some greek letters from a different package? (So as that they rest distinct from their non-variant versions.)
\documentclass[a4paper]{article}
\usepackage{lmodern}
\usepackage{eulervm}

\usepackage{amsmath, amssymb, amsfonts}

\begin{document}
Look at $\varrho$ and $\varsigma$.
\end{document}

A:

If you want to use default (i.e. Computer Modern) font of \varrho and \varsigma, you can declare using 
\DeclareSymbolFont{greekletters}{OML}{cmr}{m}{it}
\DeclareMathSymbol{\varrho}{\mathalpha}{greekletters}{"25}
\DeclareMathSymbol{\varsigma}{\mathalpha}{greekletters}{"26}

Code
\documentclass[a4paper]{article}
\usepackage{lmodern}
\usepackage{eulervm}

\DeclareSymbolFont{greekletters}{OML}{cmr}{m}{it}
\DeclareMathSymbol{\varrho}{\mathalpha}{greekletters}{"25}
\DeclareMathSymbol{\varsigma}{\mathalpha}{greekletters}{"26}

\usepackage{amsmath, amssymb, amsfonts}

\begin{document}
Look at $\rho$ and $\sigma$

Look at $\varrho$ and $\varsigma$.
\end{document}

Output

