Well, though not mentioned in the essay, Sabine Baring-Gould's
Book of Were-Wolves is available at Project Gutenberg, and is a fascinating read for anyone interested in the history and legendry concerning lycanthropy:
The Project Gutenberg EBook of The Book of Were-Wolfes, by Sabine Baring-Gould
His
Curious Myths of the Middle Ages is available here:
Internet Archive: Details: Curious myths of the Middle Ages
I recommend looking up the latter here, as most editions of the 20th century are highly abridged.
Pliny's letter to Sura can be found in any edition of his letters, but is also available here:
Pliny Book 7, Letter 27 (English)
The selections from Phlegon's On Wonderful Events, etc., were largely from Lacy Collison-Morley's
Greek and Roman Ghost Stories, which can be found here:
http://www.horrormasters.com/Collect...son-Morley.htm
Defoe's "Apparition of Mrs. Veal" can be found numerous places, such as this:
Defoe, Apparation of Mrs. Veal