Perhaps you should try some spelling variations:
toc sach » hoc sach, thuoc sach, nuoc sach
doc sach » hoc sach, nuoc sach, dac sac
vien cac » vien bach, vien dai, gian cac
tu nang » tru nang, tu nong, tu nano
cao hoc » co hoc, cho hoc, chat hoc
vien da » vien dai, hien dai
luc van » luoc van, luu van, duc van
minh vi » minh voi, dinh vi, minh va
vi cua » vai cua, di cua

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: ((toc sach) OR (doc sach)) tu nang cao hoc. lieu ((vien cac) or (vien da)) luc van minh vi cua cac~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (doc sach)) tu nang cao hoc. lieu ((vien cac) OR (vien da)) luc van minh vi cua cac*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) OR (doc sach)) tu nang cao hoc. lieu ((vien cac) or (vien da)) luc van minh vi cua cac*".