Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
cai nuoc » cap nuoc, cac nuoc, cuoi nuoc
cau tren » cu tren, dau tren, ca tren
hieu ve » hieu va, hieu van
sach ky » sac ky, sach y, sach ty
va danh » va dinh, va hanh, dia danh
ma hoi » mai hoi, xa hoi, me hoi
va dan » ca dan, va dao, va dau
vi cau » va cau, ve cau, di cau
ve cai » va cai, ve cac, ve tai

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 ky nang ((ma hoi) OR (ma hoa)). hieu ve cai nuoc ((va danh) or (va dan)) vi cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky nang ((ma hoi) OR (ma hoa)). hieu ve cai nuoc ((va danh) OR (va dan)) vi cau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ky nang ((ma hoi) OR (ma hoa)). hieu ve cai nuoc ((va danh) or (va dan)) vi cau tren".
• Adding a wildcard symbol may retrieve word variants: toc sach ky nang ((ma hoi) OR (ma hoa)). hieu ve cai nuoc ((va danh) or (va dan)) vi cau tren*.