Writing Mathematics : Linking words

I can recommend you the booklet Writing Mathematical Papers in English, Jerzy Trzeciak, EMS Publishing, http://www.ems-ph.org/books/book.php?proj_nr=34.

It contains many lists of useful expressions to borrow from.

Another option is to look at past works that have won awards, some examples can be found at:

Mathematical Association of America Writing Awards

Journal of Physics A: Mathematical and Theoretical Best Paper Prize

It looks as though many of the above papers are freely available.

I also like to read older works. Sometimes the written style and clarity is very good. One of my favourites is Investigations on the Theory of Brownian Movement, Albert Einstein. (OK I'll confess that this is a subject of interest to me). This was translated by Cowper and Edited by Furth - so the written quality is very good. I have a hard copy, but fortunately a pdf can be found at users.physik.fu-berlin.de/~kleinert/files/eins_brownian.pdf

If you are Russian, everything was done for us by A.B. Sosinsky in his great book "How to write a mathematical article in English". Here is a link (http://www.ega-math.narod.ru/Quant/ABS.htm). The book is of course in Russian. It helped me many times in my life.

Other suggestions: read other articles or find some English speaking friends to reread them after. If these friends know mathematics, even better. The friend who helps me out was studying English literature and now is doing her MD career. But her mathematical English is much better than mine!