Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
vien cac » vien bach, vien dai, vien da
sang ma » tang ma, nang ma, sang tao
truc va » thuc va, thuc vat, trung va
cua tre » cua te, cuu tre, cua triet
ma hoi » mai hoi, xa hoi, ma hoa
ve cac » va cac
va don » va dong, va doc, va do
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: doc sach _ sang ma hoi. hieu ((ve cac) or (vien cac)) truc va don vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach _ sang ma hoi. hieu ((ve cac) OR (vien cac)) truc va don vi cua tre.
• Adding a wildcard symbol may retrieve word variants: doc sach _ sang ma hoi. hieu ((ve cac) or (vien cac)) truc va don vi cua tre*.