Finding packages for TexLive

From the Ubuntu Software Center if you search for the name of the LaTeX package that you want (e.g. amsmath) you will find what you need (e.g.).

Via command line you can do the same thing with apt-cache:

apt-cache search amsmath
texlive-latex-base - TeX Live: LaTeX fundamental packages
texlive-latex-extra - TeX Live: LaTeX additional packages
texlive-math-extra - TeX Live: Mathematics packages
texlive-lang-italian - TeX Live: Italian

and then to be sure

apt-cache show texlive-latex-base
Package: texlive-latex-base

[...]

  amscls -- AMS document classes for LaTeX.
  amsmath -- AMS mathematical facilities for LaTeX.
  babel -- Multilingual support for Plain TeX or LaTeX.