In guwiki (gu.wikipedia.org), adding <math> formula like,
<math>\Delta H_{reaction}^\ominus = \sum \Delta H_{\mathrm f \,(નીપજો)}^{\ominus} - \sum \Delta H_{\mathrm f \,(પ્રક્રિયકો)}^{\ominus}</math>doesn't work,
English formula works fine,
<math>\Delta H_{reaction}^\ominus = \sum \Delta H_{\mathrm f \,(products)}^{\ominus} - \sum \Delta H_{\mathrm f \,(reactants)}^{\ominus}</math>Example article: https://gu.wikipedia.org/wiki/હેસનો_ઉષ્મા-સંકલનનો_નિયમ
(and actual error is at: https://gu.wikipedia.org/w/index.php?title=હેસનો_ઉષ્મા-સંકલનનો_નિયમ&diff=prev&oldid=502285&diffmode=source)