The category "<contact_type-sing-neutral>" can be expressed as follows:
<contact_type-point_id_type_none-sing-neutral> <air_formation_mod>
<contact_type_nom-point_id_type_none> <aircraft_activity> <contact_type-point_id_type_none-sing-simple-neutral>
<contact_type_nom-sing-neutral>
<det> <contact_type_nom-sing-neutral>
<digit-not_zero-sing> <contact_type_nom-sing-neutral>
<group_contact_id> <contact_type-point_id_type_none-sing-simple-neutral>