Using Linux Libertine fonts for math without newtxmath
The right order to load those packages is amsthm
, newtxmath
, mathspec
\usepackage{amsthm}
\usepackage[libertine]{newtxmath}
\usepackage{mathspec}
You don't need to load amsmath
since it is already loaded by newtxmath
. That's also the reason why mathspec
complains when you load newtxmath
after it.
Moreover, note that both amsthm
and newtxmath
define the \openbox
command. But, while the former defines it through a \newcommand
, the latter does it through a \DeclareRobustCommand
, so it does not complain...