Ralf, This was probably a latex macro for \[ a \mathrel{\mathop{\rightleftarrows}^{\mathrm{over}}_{\mathrm{under}}} b\]
which uses the amssymb package to create over a ---------> b <-------- under Tim _______________________________________________ Axiom-developer mailing list Axiom-developer@nongnu.org https://lists.nongnu.org/mailman/listinfo/axiom-developer