The Sybil is taught (or rather, performed in slow-motion) on the Flourishes 101 section of the Everythingelse disc of The Trilogy, by Dan and Dave, which you can buy right here on theory11. And of course, it's also taught on Youtube.
If you're starting out in flourishing, I'd recommend Genesis v1 (available on theory11) for the basics of flourishing and more,
and also the second volume of Daniel Madison's Dangerous, Motion (also available on theory11), for two-handed cuts.
And after that, I'd recommend The System (available on Dan and Dave's website) and the Flourishes disc of The Trilogy.
But when I first started flourishing, the internet (e.g. Youtube, kardistry.com) were my primary resources.
And even now I'm no expert, so this might not be the best route to take.