/*    macro                  argcnt          substitution   */
{ "\\xleftarrow",            "1", "{\\overset{#1}{\\leftarrow}}" },
{ "\\xrightarrow",           "1", "{\\overset{#1}{\\rightarrow}}" },
{ "\\xrightleftharpoons",    "1", "{\\overset{#1}{\\rightleftharpoons}}"},
{ "\\autorightleftharpoons", "2", "{\\overset{#1}{\\underset{#2}{\\rightleftharpoons}}}"},