Ostergard, Carey; Nicola, Chris (June–July 2004). "Q&A: The darkest days". National Geographic Adventure. 6 (5). New York: National Geographic Society. OCLC60657103. Archived from the original on 27 January 2010. Retrieved 25 December 2009.
Ostergard, Carey; Nicola, Chris (June–July 2004). "Q&A: The darkest days". National Geographic Adventure. 6 (5). New York: National Geographic Society. OCLC60657103. Archived from the original on 27 January 2010. Retrieved 25 December 2009.
Ostergard, Carey; Nicola, Chris (June–July 2004). "Q&A: The darkest days". National Geographic Adventure. 6 (5). New York: National Geographic Society. OCLC60657103. Archived from the original on 27 January 2010. Retrieved 25 December 2009.