Reference:Practicing HSK Grammar (语法精讲精练)
Practicing HSK Grammar (语法精讲精炼), by Sinolingua, is a rather thorough guide to the grammar appearing on the HSK (old HSK Intermediate). Althoguh there is now a new HSK, the grammar patterns covered here remain more or less the same. This book covers most of the grammar patterns A2-B2 in difficulty.