FIDE Trainers' Commission (TRG) Trainers' Surveys
From year 2010 to date, the FIDE Trainers' Commission (TRG) regularly publishes high quality chess training materials (in pdf format in English language) in the form of Trainers' Surveys, targeted at improving chess understanding.
Please see a reflection on FIDE Trainers' Commission work, published at http://en.chessbase.com/post/fide-trainer-a-treasure-of-articles