Found the following HTML validation problems:
math_to_rd.html:82:795 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:82:1030 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:82:1116 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:82:1201 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:82:1314 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:82:1502 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:82:1803 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:82:2040 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:93:161 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:93:116 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:93:94 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:93:243 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:93:291 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:93:216 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:93:393 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:93:610 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:93:567 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:93:545 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:93:651 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:93:923 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:93:1129 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:93:1341 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:93:1545 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:93:1593 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:93:1516 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:93:1703 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:93:1988 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:93:1944 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:93:1922 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:93:2029 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:93:2171 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:93:2382 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:93:2629 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:93:2677 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:93:2600 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:93:2788 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:93:3163 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:93:3119 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:93:3097 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:93:3204 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:93:3503 (math_to_rd.Rd:47): Warning: trimming empty <span>
math_to_rd.html:104:377 (math_to_rd.Rd:59): Warning: trimming empty <span>
math_to_rd.html:104:499 (math_to_rd.Rd:59): Warning: trimming empty <span>
math_to_rd.html:104:585 (math_to_rd.Rd:59): Warning: trimming empty <span>
math_to_rd.html:104:670 (math_to_rd.Rd:59): Warning: trimming empty <span>
math_to_rd.html:104:1040 (math_to_rd.Rd:59): Warning: trimming empty <span>