“There are many famous books about Heiho, military strategy, and one of them is the Sanryaku三略. The Sanryaku is, as the Kanji in the name state, three stratagem. The Jo, Chu and Ge, or upper, middle and lower. While some Densho have a Shoden, Chuden and Okuden with the Shoden being the easiest and the Okuden/Okugi being the hardest the Sanryaku is divided into three sections not based on level. The Jo no Maki, or upper book should not be considered to be any “easier” or “harder” than the middle or lower books.”
More on this book in English here.
“The Joryaku of Gyokko Ryu is taijutsu where both are unarmed. The Churyaku deals with doing Mutodori against a short sword/knife while the Geryaku no maki has Muto dori against an opponent armed with a Katana. Each scroll is important in its own right and, just like the Sanryaku, should not be thought in terms of levels. It is important to keep this difference in mind when training Gyokko Ryu.”