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

<specific_platoon_type-creatable-sing>

155mm howitzer

<i_f_v-sing>

122mm howitzer

152mm howitzer

2s1 122mm howitzer

2s1 howitzer

2s3 152mm howitzer

2s3 howitzer

swa 122mm howitzer

swa 152mm howitzer

swa 2s1 122mm howitzer

swa 2s1 howitzer

swa 2s3 152mm howitzer

swa 2s3 howitzer

<specific_vehicle_type-sing>

155mm howitzer

<i_f_v>

122mm howitzer

152mm howitzer

2s1 122mm howitzer

2s1 howitzer

2s3 152mm howitzer

2s3 howitzer

swa 122mm howitzer

swa 152mm howitzer

swa 2s1 122mm howitzer

swa 2s1 howitzer

swa 2s3 152mm howitzer

swa 2s3 howitzer

<specific_vehicle_type-creatable-sing>

155mm howitzer

<specific_platoon_type-not_creatable-sing>

155mm howitzer

<specific_vehicle_type-not_creatable-sing>

155mm howitzer

<specific_platoon_type-sing>

155mm howitzer

<specific_vehicle_type-not_creatable>

155mm howitzer