If you have not yet had a chance to visit our e-books, you should consider doing so. They are basically fluid power textbooks offered for free.
We launch a chapter per month and we are currently up to Chapter 20 of our second e-book, Fluid Power Circuits Explained. This chapter explains Sequencing Valves.
We have a wealth of free content on our website found at www.hydraulicspneumatics.com so please go there and let me know what you think.