Columbia subject headings:
Emergency communication systems--Law and legislation--United States.
Telephone--Emergency reporting systems--Law and legislation--United States.
Wireless communication systems--Law and legislation--United States.
Harvard subject headings:
Emergency communication systems--Law and legislation--United States.
Telephone--Emergency reporting systems--Law and legislation--United States.
Wireless communication systems--Law and legislation--United States.
Princeton subject headings:
Emergency communication systems--Law and legislation--United States.
Telephone--Emergency reporting systems--Law and legislation--United States.
Wireless communication systems--Law and legislation--United States.