Hi, I'm not a practitioner of ninjutsu and I don't practise any martial arts at the moment. However, I am interested in the history of covert operations in diverse cultures, including Japan. I don't know any Japanese language and I'm just interested in this for its own sake.

So far, I have identified three books, or scroll collections, that can be assumed to be old manuals about the ninja. They are:

1) Shoninki
2) Bansenshukai
3) Ninpiden

What I'm after are some reliable (and complete) translations of these works. I understand only a few original manuscripts are in existence and that there may be slight differences between them, but I expect they are substantially the same.

When looking for these books, I discovered a lot of interesting and sometimes heated forum posts and remarks made by people familiar with this subject matter. I gather there are serious problems with regard to translation accuracy, translations of translations, uncited authors(!), plagiarism and worse. Therefore, as someone who doesn't have a background in this field, I am wary about which books to buy. Academic-style footnotes would inspire confidence but wouldn't be necessary for me if the translator is someone properly credentialed in either the ninjutsu tradition or research/linguistics.

My first question is probably the easiest: are Claude Schedler's, Don Roley's and Axel Mazuer's translations of the Shoninki fairly reliable (I think I can narrow my choice to these three authors, and I'm not going to ask which is "best")? Reliable as in accurate, complete and not redacted.

Second, the Bansenshukai seems to be a lengthy text, and at least some of it is available online in Japanese (not much use to me). However I'm pretty sure not all of the text in this book has been reproduced online. And I'm absolutely sure that most of the English translation of this work online omits reams of content. Is a reliable translation of this book available yet, and if so where can I get it?

Finally, is there a good Ninpiden translation available?

Thanks for any tips.