This balanced corpus (in abbreviation CAJA) of academic language was created ny Iztok Kosem in 2010, for more information, see his PhD thesis. The corpus has 83,5 million words and consists of 13,116 articles from 28 different disciplines.
Kosem, Iztok. Designing a model for a corpus-driven dictionary of Academic English. PhD Thesis. Aston University, 2010.