In Hong Kong Bird Report 1988, p.74 - 77 (search for P.39 in PDF file), describing the record of Mountain Hawk Eagle.
It said something about identifying Crested Honey Buzzard and Serpent Eagle.
Still feel confused after reading it, anymore comment and help?
http://www.hkbws.org.hk/web/chi/documents/bird_report/1988_birdreport_protected.pdf