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ISKCON’s Changes to Srila Prabhupada’s Bhagavad-gita As It Is and Perfect Questions, Perfect Answers (by Madhudvisa Dasa).
Perhaps the first book on the book changes. So old it was made with a typewriter. Definitely of both present day and historical value. It contains a lot of good evidence against the changes, good arguments and historical documentation (like mails).
Download the book here: ISKCON’s Changes to Srila Prabhupada’s Bhagavad-gita As It Is and Perfect Questions, Perfect Answers (by Madhudvisa Dasa).
Arsa-Prayoga 
Is this Book als printed of only for download?
It is so old that I do not think it exists in printing.