Perhaps you should try some spelling variations:
doc sach » toc sach, nuoc sach, dac sac
nam thuc » nam thuoc, am thuc, nam thu
cau theo » cau thi, cau tao
hoc sach » hoc sinh, hoc cac, hoc anh
ky lang » ky nang, ky tang, tay lang
ky dang » ky nang, ky danh
hieu va » lieu va, hieu qua
thuc va » thuc vat, thuc dan, thuc day
dau vai » dau va, dau hai, dau tai
vai cau » va cau, van cau, vai cac
va nam » van nam, ha nam, va nay
va dau » va dao

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((doc sach) or (hoc sach)) ((ky lang) or (ky dang)) xa hoi. hieu va nam thuc va dau vai cau theo~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((doc sach) OR (hoc sach)) ((ky lang) OR (ky dang)) xa hoi. hieu va nam thuc va dau vai cau theo.
• Adding a wildcard symbol may retrieve word variants: ((doc sach) or (hoc sach)) ((ky lang) or (ky dang)) xa hoi. hieu va nam thuc va dau vai cau theo*.