Perhaps you should try some spelling variations:
va triet » va thiet, va trien, ve triet
cham loc » cham soc, chon loc, cham o
dua tren » dung tren
sach thu » sach thue, sach thieu, sach tham
hanh va » hang va, hanh vi
va hanh » van hanh, va thanh, va danh
sach ty » sach y, sach tu, xach tay
hieu va » lieu va, hieu qua
nang ma » tang ma, sang ma, nang cao
va cham » va chat, va tham
loc va » hoc va, luc va

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu ((sach ty) OR (sach thu)) nang ma hoa. hieu va cham loc va hanh va ((dua tren) or (va triet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach ty) OR (sach thu)) nang ma hoa. hieu va cham loc va hanh va ((dua tren) OR (va triet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach ty) OR (sach thu)) nang ma hoa. hieu va cham loc va hanh va ((dua tren) or (va triet))".
• Adding a wildcard symbol may retrieve word variants: tu ((sach ty) OR (sach thu)) nang ma hoa. hieu va cham loc va hanh va ((dua tren) or (va triet))*.