ISBELL, Douglas. MISSIONS TO GATHER SOLAR WIND SAMPLES AND TOUR THREE COMETS SELECTED AS NEXT DISCOVERY PROGRAM FLIGHTS [online]. Washington, DC: NASA, 1997-10-20, [cit. 2008-08-25]. Dostupné online. Archivované 2009-10-28 z originálu. (anglicky)
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ISBELL, Douglas. MISSIONS TO GATHER SOLAR WIND SAMPLES AND TOUR THREE COMETS SELECTED AS NEXT DISCOVERY PROGRAM FLIGHTS [online]. Washington, DC: NASA, 1997-10-20, [cit. 2008-08-25]. Dostupné online. Archivované 2009-10-28 z originálu. (anglicky)