Digit Magazine Question

I am a DIGIT Reader since 06 , but Unfortunately i had missed a few (on or two in a year)
Subscriber since (a few months)
Recently i was rearranging and found out that i had the

Encyclopedia Technica Series

Vol - 3 (Dec 2013)
Vol - 5 (Dec 2014)

I dont have
Vol - 1 (Dec 2012)
Vol - 2 (June 2013)
Vol - 4 (June 2014)

I would like to have the rest of them , by have i mean BUY the hard copy from Digit

I want to know that can i buy the books only without buying the magazines of those month .
or i have to buy those magazines of those months to get them ?
Please Reply.

Are digital Copy Available for those volumes ?

I was unsure as to the subsection i should put this . So please Transfer this to the Proper section.