for math fonts. not only "one" character but (for example) all letters.
– mertOct 19 '13 at 12:25
@mert: There's no technical difference for one character or many. Every single symbol in math mode is defined separately.
– Leo LiuOct 19 '13 at 12:38
i found something: this gives letters -palatino, others -times n.r. \usepackage{mathptmx}
\usepackage{avant}
\DeclareSymbolFont{letters}{OML}{pxmi}{m}{it}
– mertOct 19 '13 at 14:46