Pure tesuji / tsumego problem books do not need text; they can be in any language. All the reader needs to understand is a variation's outcome and this is easy enough without comments. Positional judgement or middle game problems are harder without text.

The forum rules answer your question but... you are interested in a more specific discussion of what is advertisement and what is allowed. Maybe better in a different thread, but since you asked here, for the time being I reply here.

Why do you ask about me? You can also ask whether other people's signatures about their products or teaching are possible or prohibit them from writing in this forum? (Do you mean the "Amateurs" forum?)

What surprises me the most is that you choose this thread (Why not the joseki thread) for discussing your question, a thread in which I only stated "Therefore I teach all move types instead of only tesuji types.". This is my "advertisement" for what I think everybody should do: to teach all move types instead of only tesuji types. All moves are important - the tesujis are not the only important moves.

Robert certainly hasn't made it personal this time.

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Occupy Babel!

You're absolutely right.
Actually I wanted to say something like "easily accessable books for westerners" or anything similar, but it turned out to become "english books"...

The main problem in learning tesuji (and life and deat, too) is that you have to practice a lot. Much more than one or two games on KGS a week would provide. So it's practically inevitable to read books on the topic. But just learning from huge problem collections (like "501 tesuji problems") is very hard, especially when you want to understand the underlying structure (compare Robert's approach to joseki).
So beginning with book like "Tesuji" from Davies is essential to understand what you're actually practicing. But to polish your skills, you have to do thousands of thousands of problems no matter how good you understand the tesuji itself.

And practising during games is really hard. Some weeks ago a german 5dan told me to improve my reading, as this my current main weakness. So I started to do lots of tsumego, of course, but I also try to read as much as possible during games. This is very tiring, but in the end you have to apply the tesuji you learned from books and, even more important, have to know when they can't be applied.

So for conclusion, the best way to learn tesuji, I think, is to switch from theoretical books to problem collections to intense in-game reading.

This is the dan player's "standard".

If it's standard, then it's good, right?

You don't have to be good at any particular skill to become a dan player, but you have to be good at some skill. And it does not have to be a go skill. I know someone who is a dan player because he refuses to lose.

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The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

Apply your earlier conclusion "switch from theoretical books to problem collections to intense in-game reading." and when you are dan you don't count in hundreds any longer but in thousands. Up to about 3d, 1000 might be enough though if you have other strengths.