Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
toc sach » hoc sach, doc sach, thuoc sach
nang hoc » nang doc, nang luc, dong hoc
hoc khoi » hoc khoa, hoc hoa, hoc noi
dao van » do van, dang van
tu sach » thu sach, su sach, te sach
hieu va » lieu va, hieu qua
dao va » tao va, do va, cao va
cac su » cach su, cac sau, cac du
su va » su van, tu va

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((tu sach) or (toc sach)) ky nang hoc khoi. hieu va cac su va ((dao va) or (dao van)) cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (toc sach)) ky nang hoc khoi. hieu va cac su va ((dao va) OR (dao van)) cau tren.
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (toc sach)) ky nang hoc khoi. hieu va cac su va ((dao va) or (dao van)) cau tren*.