The ASCA Data Reduction Guide by NASA HEASARC

Version 2.0; also called the ABC Guide. Institutional technical source, ASCA Guest Observer Facility, NASA/Goddard. Section 4, SIS Issues: heasarc.gsfc.nasa.gov/docs/asca/abc/node5.html

§4.7 gives the Fano factor, read-noise contribution and FWHM energy-resolution expression; the numerical detector examples are ASCA-specific, not universal CCD specifications.