Perhaps you should try some spelling variations:
thuoc sach » hoc sach, nuoc sach, thuat sach
cac truc » cau truc, cac tru, cac trung
hieu van » hieu va, thien van, lieu va
dan dai » dat dai, can dai, dan dat
truc va » thuc va, thuc vat, trung va
van cac » van hac, van cau, van bac
cua tre » cua te, cuu tre, cua triet
nang ma » tang ma, sang ma, nang cao
nang xa » nang x, lang xa, mang xa
va dan » ca dan, va dao, va dau

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((thu hoach) or (thuoc sach)) ky ((nang xa) OR (nang ma)) hoi. hieu van cac truc va dan dai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((thu hoach) OR (thuoc sach)) ky ((nang xa) OR (nang ma)) hoi. hieu van cac truc va dan dai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((thu hoach) or (thuoc sach)) ky ((nang xa) OR (nang ma)) hoi. hieu van cac truc va dan dai cua tre".
• Adding a wildcard symbol may retrieve word variants: ((thu hoach) or (thuoc sach)) ky ((nang xa) OR (nang ma)) hoi. hieu van cac truc va dan dai cua tre*.