Who write grammar books

This is perhaps not exactly what you mean, but i found this book very helpful: English Grammar for Students of French. The same publishing house, apparently, produces English Grammar for Students of Latin and English Grammar for Students of Italian (first i'd heard of it).

Grammar and other text books about a language, intended for students who are speakers, native or otherwise, of another language are common. They are a very necessary thing.

My wife and I are currently working our way through a Catalan course and one of our books is Catalan: A Comprehensive Grammar by Max Woodfield Wheeler, Alan Yates (who are native English speakers) and Nicolau Dols Salas (who is a Catalan). Such a collaboration is quite common. It is one of the well known Routledge Comprehensive Grammars which cover a large number of languages:

http://www.routledge.com/books/series/SE0550/

We have both the printed book and the PDF version. A sample:

1.1.7 GENDER OF ANIMAL NAMES For the most part, only familiar or domestic animals and birds have separate forms for the male and the female of the species. Some of these, where the masculine and feminine words are unrelated, such as cavall (m.) ‘horse’, ‘stallion’, egua (f.) ‘mare’, have been mentioned above (1.1.4). Those where the masculine form is derived from the feminine with the suffix -ot were listed at 1.1.3, and feminines with special suffixes at 1.1.2. The remaining cases of animal names where a regularly formed masculine and feminine pair exists are these: ànec (m.) ànega (f.) duck cérvol (m.) cérvola (f.) stag/doe colom (m.) coloma (f.) pigeon, dove

Also we find "Grammaire et vocabulaire du catalan" by Eric Freysellinard quite interesting (I got this for 3 euros in a second hand bookshop in Perpignan). There are Catalan grammars that we have seen for speakers of German, French, Italian, Castellano ("Spanish"), and probably most European languages. Catalan is spoken by a comparatively small number of people; for more widely spoken languages there will be more languages in which grammar books are available.

Thank you~

But to learn a foreign language, why not directly read grammar books etc written by native speakers of that language? How can we make sure that native English speaker did not learn the wrong thing regarding French, German, Italian, Spanish etc.?

How can we be sure that a native speaker of French, German, Italian or Spanish has correctly stated the case in English, or in Mandarin, for that matter?

Easy question. I've learned English for a long time, I never worry about learning a construction wrongly used by native speakers, because I can always produce evidence that native speakers use it that way. It would be extremely difficult for other native speakers to refute that native speaker.

It is very easy to to hear if another native speaker is making a grammatical mistake. Is s/he making a mistake or is it dialect.? Where I come from the dialect is " Give the book to he or she" It sounds just awful and if you use it a few miles away it would be seen as a mistake.
I have seen and refused to work with a book about Swedish. It is written by a native speaker as well as a not native speaker. There are grammar mistakes,
historical mistakes, how to behave mistakes and wrong information regarding food and traditions.
A non native speaker with good knowledge about Sweden and Swedish would have done a much better job.

I see--so if you have a book on, for example, English grammar, you take it around to native English speakers to have it vetted? There are a lot of native English speakers where you live?

Native speakers of a language routinely dispute what other native speakers claim.

It sounds like WBYeats wants grammar text books to be 'rule books'.

"incorrect things regarding ... "

You can't be sure. This illustrates one of the major problems of teaching by 'grammar' [and by translation].

Students mistakenly think that they can learn a language by focusing on grammar rules. These rules are so spare in their nature whereas the rules that actually describe any language are immense in number.

Little children, of any language, learn the rules, that immense number, with no difficulty at all. Foreign scholars learn with great difficulty and often are unable to function in the target language.

The complexity of language also ensures that any learner of any language, especially one focused at the grammar level will come away with mistakes, how many mistakes depends on a number of factors.