my %allowed_text_code = ('$\\alpha$'     => 'α',
                         '$\\beta$'      => 'β',
                         '$\\gamma$'     => 'γ',
                         '$\\delta$'     => 'δ',
                         '$\\theta$'     => 'θ',
                         '$\\pi$'        => 'π',
                         '\\degrees'   => '°'
                         );