The original description of the subspecies Acanthophis pyrrhus armstrongi by Wells and Wellington from 1985 (as a full species).
The above was from page 43 of the paper - Wells, R.W. and Wellington, C.R. 1985. 'A classification of the Amphibia and Reptilia of Australia', Australian Journal of Herpetology, Supplementary Series, (1):1-61. Reproduced here with permission of the senior author.
For the full text of this paper and other major taxonomic works by Richard Wells and Cliff Ross Wellington as well as over 100 definitive papers on Australian herpetology by Raymond Hoser and other top-name herpetologists, get hold of a copy of the "Hoser Wildlife Collection CD-rom" - Australia's leading herp CD-rom
For the webpage with the text of the Hoser (1998) revision of Australasian Death Adders