Ratio value hands vs bluffs

i'm interested to know: who says that one should have this ratio OTF? one of the major poker schools/cpoaches?

Yes, don't understand? I have seen in more than one resources.
OTF 66%
OTT 50%
OTR 33%

Depends usually the same or 1:1 is ok

It depends also what kind of limit you are playing what kind of ratio is good.
On NL2 for example bluffing isn't a great idea against most villains.

Cheers,
SDK1987

it's just interesting that major poker coaches would give such flawed advice - there is no rule of thumb for this, as a) it depends on SPR and sizings and equities of continuing hands, and b) the concept 'bluff' just isn't very useful or applicable on the flop as opposed to on the river - instead it's rather misleading.
on the river things are relatively easy to understand, but what is a flop valuehand? what does that mean?

Google for this:
How to Win More Chips with Your Bluff-to-Value Ratios

Then you will find an articel from upswing Poker. Maybe this articel helps you.

(I dont know if it is allowed to post the direct link here.)

Value to Bluff Check Raising the Flop
1:1.5 - 1.:2
The more equity your value hands have the more you are able to bluff. Likewise, the more equity your bluffs have the more you are able to bluff. There is a lot of math and variables that go into this, and they largely depend on board texture. 1.5-2 bluff raises per value raise is a good general rule of thumb.

When you are value betting draws, because your equity is worse without SDV, you should bluff much less (1 bluff for every 2 draw value combos).