Perhaps you should try some spelling variations:
toc sach » hoc sach, thuoc sach, nuoc sach
doc sach » hoc sach, nuoc sach, dac sac
tang xa » trang xa, tang ma, lang xa
dan vai » dan va, dan tai, dan vat
hieu va » hieu qua
ky tang » ky nang, ky dang, kho tang
cu tren » tu tren, dua tren
nam tu » nam thu, nam thuc
va dan » ca dan, va dao, va dau
vai cu » vai cua, van cu

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)) ky tang xa hoi. ((hieu va) or (lieu va)) nam tu va dan vai cu tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (doc sach)) ky tang xa hoi. ((hieu va) OR (lieu va)) nam tu va dan vai cu tren.
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (doc sach)) ky tang xa hoi. ((hieu va) or (lieu va)) nam tu va dan vai cu tren*.