As of HEASoft Version 6.21, xselect supports extraction of data products from the following missions:
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ASCA, ASTROSAT,  AXAF, BBXRT,  EINSTEIN,  EXOSAT,  HITOMI,  INTEGRAL,  NICER,  NUSTAR,  ROSAT,  SAX,  SPECTRUM-RG,  SUZAKU,  SWIFT,  XMM,  &amp; XTE