Fire and Smoke Attributes Where do I find the attributes available for the fire rendering at Cycles (flame, color, density...). Where is the list? or at least, how do I find which ones are available? They are not listed in the custom variables (says it's blender's programming api? are they hidden?).

Everybody talks about them but I'm not able to find them, even on the official guide at blender.org. In fact, the help pages are outdated and contain nothing about the fire and smoke and fire modes for smoke dynamics and the parameters.

This question is, in fact, a general question:
Where do I find the attributes available?.

For reference: 
http://www.blender.org/manual/physics/smoke/flow_object.html
There you can see it is always referencing a particle system. But in the volumes you have the smoke and fire AND fire options. Why doesn't it talk about it?

I'm using blender 2.74
You can find that Attributes on the official Page for the Attribute Node:
Attribute Node - Blender Manual

Or on the Stack Exchange Thread: All Possible Attributes - Stack Exchange