The eBook can be purchased online
 through these sites:


24Symbols
Amazon
Apple
Barnes & Noble Nook
BibliU.com
Bookmate
Booktopia
De Marque Retail
eBooks.com
Hummingbird DM
ITSI Education UK
Kobo
Libreka
Libri
LitRes eBook
LIX
RedShelf (Virdocs)
SpoonRead
VitalSource
Wook