mml=<math xmlns="http://www.w3.org/1998/Math/MathML"><mstyle mathsize="12px"><mrow><mi>dM</mi><mo>=</mo><mfenced separators="|"><mfrac><mi mathvariant="normal">M</mi><mi mathvariant="normal">L</mi></mfrac></mfenced><mi>dx</mi><mo>'</mo><mi>dM</mi><mo>'</mo></mrow></mstyle></math>