Describe the bug
cfecmdmnems:6: warning: Illegal command \dd as the argument of a \dd command ....
....
cfetlmmnems:211: warning: Illegal command \SB_PIPEOPTSEC as the argument of a \c command

To Reproduce
Steps to reproduce the behavior:

1. make usersguide

System observed on:

• Hardware
• Ubuntu 18.04
• doxygen 1.8.13

Reporter Info
Anh Van, NASA Goddard