"Province: ILOCOS SURArchived 2016-04-17 at the वेबैक मशीन". PSGC Interactive. Makati City, Philippines: National Statistical Coordination Board. Retrieved 23 September 2013.
"Province: ILOCOS SURArchived 2016-04-17 at the वेबैक मशीन". PSGC Interactive. Makati City, Philippines: National Statistical Coordination Board. Retrieved 23 September 2013.