Calling San Marino from the United States explained:

• 011 - US exit code; dial first for international calls made from the USA or Canada
• 378 - Country Code for San Marino
• Phone Number - mostly 10 digits for landlines and 8 digits for mobile numbers/VoIP phones
• US to San Marino landlines international dialing format: 011 378 0549 ??? ???

How to dial to San Marino cellular:

• dialing format for calls to a cell phone: 011 378 6? ??? ???
• residents of San Marino often use cell phone numbers registered in Italy (10 digits, 3 is the initial digit)

Phone Books:

• Pagine Gialle - Italian Yellow Pages, includes San Marino
• Pagine Gialle & Bianche - Yellow and White Pages, in Italian