The rules that use the vocabulary item "n a" are:

<nlb-careful>

n a

<nlb-not_command_or_system_utterance_or_user_response>

n a

<nlb-nlb7>

n a

<nlb-not_careful-nlb7>

n a

<nlb-nlb8>

n a

<nlb-not_careful-nlb8>

n a