Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
sach ky » sac ky, sach y, sach ty
va danh » va dinh, va dan, dia danh
va hanh » van hanh, va thanh, ban hanh
hai cuc » tai cuc, hai cua, thai cua
cua tre » cua te, cuu tre, cua triet
hai xuc » hai xu, chat xuc, hai huoc
lang ha » long ha
ky lang » ky nang, ky dang, ky tang
ha hoi » hoa hoi, ha noi, xa hoi
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 ky lang ha hoi. hieu qua ((hai xuc) OR (hai cuc)) ((va hanh) or (va danh)) vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach ky lang ha hoi. hieu qua ((hai xuc) OR (hai cuc)) ((va hanh) OR (va danh)) vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc sach ky lang ha hoi. hieu qua ((hai xuc) OR (hai cuc)) ((va hanh) or (va danh)) vi cua tre".
• Adding a wildcard symbol may retrieve word variants: doc sach ky lang ha hoi. hieu qua ((hai xuc) OR (hai cuc)) ((va hanh) or (va danh)) vi cua tre*.