Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
sach ly » sach y, sach lo, sach ty
hieu va » lieu va, hieu qua
so sach » so sanh, bo sach, co sach
hieu ve » hieu van
nang ma » tang ma, sang ma, nang cao
ly nang » ky nang, ly hang, ly vang
ma hoi » mai hoi, xa hoi, ma hoa
xac va » tac va, ac va, bac va
vi cau » va cau, ve cau, di cau

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach ly nang ma hoi. ((hieu ve) OR (hieu va)) cam ((xac va) or (duc va)) hanh vi cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ly nang ma hoi. ((hieu ve) OR (hieu va)) cam ((xac va) OR (duc va)) hanh vi cau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ly nang ma hoi. ((hieu ve) OR (hieu va)) cam ((xac va) or (duc va)) hanh vi cau tren".
• Adding a wildcard symbol may retrieve word variants: so sach ly nang ma hoi. ((hieu ve) OR (hieu va)) cam ((xac va) or (duc va)) hanh vi cau tren*.