Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
vu sach » vu bach, su sach, vu khach
thuc va » thuc vat, thuc dan, thuc day
va nham » va cham, va tham, va nha
hieu va » lieu va, hieu qua
cua tre » cua te, cuu tre, cua triet
thu va » thue va, tu va, thu ha
vi cua » vai cua, di cua
x hoi » xa hoi, o hoi, x ho

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((vu sach) or (toc sach)) ky nang x hoi. hieu va nham ((thu va) OR (thuc va)) hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((vu sach) OR (toc sach)) ky nang x hoi. hieu va nham ((thu va) OR (thuc va)) hanh vi cua tre*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((vu sach) or (toc sach)) ky nang x hoi. hieu va nham ((thu va) OR (thuc va)) hanh vi cua tre*".