The category "<basic_nl_command>" can be expressed as follows:

<basic_nl_command>

<system_operation>

<unit-pl> <commander_phrase> <unit_command-group_subj_ok>

<unit-pl> <unit_command-group_subj_ok>

<unit-sing> <commander_phrase> <unit_command>

<unit-sing> <unit_command>

<unit_command>