str_label_stress_state1="Fixed element \n(\N{GREEK SMALL LETTER SIGMA}\N{LATIN SUBSCRIPT SMALL LETTER X}\N{SUBSCRIPT ZERO}, \N{GREEK SMALL LETTER TAU}\N{SUBSCRIPT ZERO})"
# NB: no subscript of latin y, so use gamma (very similar in the display)
str_label_stress_state2="Fixed element \n(\N{GREEK SMALL LETTER SIGMA}\N{Greek Subscript Small Letter Gamma}\N{SUBSCRIPT ZERO}, -\N{GREEK SMALL LETTER TAU}\N{SUBSCRIPT ZERO})"