The following are a few references you might want to look at.

• Part 97 of the FCC Rules (part of Title 47 of the US Code of Federal Regulations) authorizes the Amateur Radio, Amateur Satellite and Radio Amateur Emergency Services.
  
• The ARRL Public Service Communications Manual (PSCM) describes the ARRL field organization which includes the Amateur Radio Emergency Service (ARES) and it's relationship to RACES as well as the National Traffic System (NTS) which is used for routing formal written message traffic via the airwaves (Radiograms).
  
• The ARRL Operating Manual (available from the ARRL catalog sales department as well as from most amateur radio booksellers) has sections that cover many aspects of amateur radio including emergency communications.