Great link!
Secret to rise your average... improve control of the second ball! That's all you need to know, seems simple but it will take hours and hours of practice...
Well, in my case, I have been practising them, not hours and hours, but more like decades and decades LOL. And I am still to improve or get any better
In my personal opinion, for most players (up to around 1.00 average), the REAL progress to better averages will yield by learning
kiss avoidence/prevention (*** Now I do not know if "kiss" is the right terminology, as I am not familiar with billiard terms in the English language

Basically I mean, the obstruction of your ball by the second ball, on the path to the third ball)
Position play, in other words, knowing what kind of a path the second ball would take, of course will help on increasing averages. It is not too hard to learn the path of the second ball (the ball that is being hit) In fact, I think that, players who come from pool-to-carom will have a know-how advantage, as they can have an idea as to where they can place the second ball. But overall, even tiny, millimetric differences in angles and position of balls can make a huge difference in the availability of shots. Most important for any player to improve is, position play, but equally or in fact MUCH MORE so, is learning kiss avoidence!!
When we watch top 3C players, their balls will hardly ever kiss! Each and every time, we see that 2nd ball will hardly ever come around, or that it leaves the same cushion slightly later/earlier or different angles from your ball, and thus the kiss is avoided. Sometimes, even if there is a small chance of a kiss in a particularly easy looking shot, pro players rather try the harder option with a less likely chance of kiss. And I don`t know if a book or a chapter thereof exists in learning kiss prevention. But IMO, this is not something that is learnable from a book. It is just practise...observation.
I think, pool-to-carom players do have an upper hand in kiss prevention. This is something where the game of pool owns 3C
Just like, how comfortable 3C players would be in terms of controlling and positioning the CB :wink: