Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
va danh » va dan, va hanh, dia danh
doi cua » dai cua, hoi cua
va dinh » van dinh, va kinh, va tinh
van lam » van nam
lam duc » lam duoc, pham duc, nam duoc
nang o » nang co, nang ho, nang ro
cua te » cua tu
o hai » co hai, so hai, o lai

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 (thu hoach)) ky nang o hai. hieu van lam duc ((va danh) OR (va dinh)) doi cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (thu hoach)) ky nang o hai. hieu van lam duc ((va danh) OR (va dinh)) doi cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) or (thu hoach)) ky nang o hai. hieu van lam duc ((va danh) OR (va dinh)) doi cua te".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (thu hoach)) ky nang o hai. hieu van lam duc ((va danh) OR (va dinh)) doi cua te*.