Citations-"Puerto Rico." Worldmark Encyclopedia of the States. Gale, 2007. Student Resources in Context. Web. 4 Apr. 2014.
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"Puerto Rico." Britannica School. Encyclopædia Britannica, Inc., 2014. Web. 5 May 2014. .

http://www.countryreports.org/country/PuertoRico/economy/transportation.htm>.