Perhaps you should try some spelling variations:
cac truc » cau truc, cac tru, cac trung
thi hanh » thi thanh
van hanh » van thanh, ban hanh, van anh
sach thi » sach thu, sach tai, sach thieu
tu sach » thu sach, su sach, te sach
hieu va » lieu va, hieu qua
hanh ma » hanh mau, hanh may, hanh va
va hanh » va thanh, va danh, ban hanh
ma hoi » mai hoi, xa hoi, ma hoa
lam va » nam va, lam ha, am va
dam va » dam van, nam va, dam ha

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 thi hanh ma hoi. hieu va cac truc ((va hanh) OR (van hanh)) ((lam va) or (dam va)) trien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach thi hanh ma hoi. hieu va cac truc ((va hanh) OR (van hanh)) ((lam va) OR (dam va)) trien.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach thi hanh ma hoi. hieu va cac truc ((va hanh) OR (van hanh)) ((lam va) or (dam va)) trien".
• Adding a wildcard symbol may retrieve word variants: tu sach thi hanh ma hoi. hieu va cac truc ((va hanh) OR (van hanh)) ((lam va) or (dam va)) trien*.