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

<det-indef>

a

<scale_number>

a thousand

a hundred thousand

<i_f_v-sing>

37mm triple-a

57mm triple-a

brdm with a t

<i_f_v-pl>

brdms with a t

<defensive_position_phrase>

a <defensive_position_phrase-not_det-sing>

<concealed_position>

a <concealed_position-not_det-sing>

<det-sing>

a

<det-indef-sing>

a

<firing_rate_measure>

rounds a minute

<i_f_v>

37mm triple-a

57mm triple-a

brdm with a t

brdms with a t

<det-not_other-indef-sing>

a