<<< mml $$\underset{\mathrm{x}}{\mathrm{BASE}}=\underset{\phantom{1}\mathrm{x}\phantom{1}}{\mathrm{BASE}}$$ >>> native [ EUnder False (EIdentifier "BASE") (EIdentifier "x") , ESymbol Rel "=" , EUnder False (EIdentifier "BASE") (EGrouped [ EPhantom (ENumber "1") , EIdentifier "x" , EPhantom (ENumber "1") ]) ]