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
truc va » thuc va, thuc vat, trung va
van cac » van hac, van cau, van bac
lang xa » lang ha, dang xay, lang van
ky lang » ky nang, ky dang, ky tang
cua tre » cua te, cuu tre, cua triet
dan di » danh di, dan de, dan li
dan da » dan dat, dan ca, dan va

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