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

<hour-not_initial_zero>

four

one four

<specific_platoon_type-creatable-sing>

brdm2 recon four

<hour>

four

oh four

zero four

one four

<digit-not_zero>

four

<digit-pl>

four

<digit_zero_to_five>

four

<digit>

four

<digit-not_zero-pl>

four

<specific_platoon_type-not_creatable-sing>

brdm2 recon four

<up_to_six>

four

<specific_platoon_type-sing>

brdm2 recon four