In your ebook, you showed different schematic symbols. Are these symbols from ISO standards or from ANSI standards? Those pilot operated valves look different from what I see somewhere else.

As I said in answer to your last question"

"That is why I call the symbols in Ch.4 "Frequently Used Symbols" since they represent all the ones Ive come across over the years. I tried to note the ones that were not strictly ISO."

Where is the place that publish and sell a sheet that include all hydraulic schematic symbols? Thanks.

The ISO symbol sets, 121901 and -2 can be purchased here:
http://www.iso.org/iso/home.htm
and search for Fluid Power Symbols.

Dito here:
http://webstore.ansi.org/

A Google search for "Fluid Poower Symbols" brought up severallinks to freebies also.

No matter which set of symbols you find there will never be a symbol for EVERY FLUID POWER COMPONENT EVER MADE. However, most use the available information to make a symbol for a new component as they see it. The problem with that is, six different people drawing such a symbol would come up with six different ones and all the College of Hard Knocks Experts would have a debate for years on which one is right.

That is the real world of the Utrained/Educated Fluid Power discipline and will continue to be as long as the system remains as is.