Butler, J. Earth Observing Systems XI. SPIE Digital Library.
Chicago-čujuhus (17. p.)Butler, James. Earth Observing Systems XI. SPIE Digital Library.
MLA-čujuhus (9. p.)Butler, James. Earth Observing Systems XI. SPIE Digital Library.
Muitte dárkkistit čujuhemiid riektatvuođa, ovdal go geavahat daid iežat deavsttas.