Perhaps you should try some spelling variations:
thien van » thi van
thanh vi » hanh vi, thanh va, thanh ve
dau tren » dau tien, dat tren, dau tieng
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
duc ban » duc van, dua ban, duc man
vi dau » vi dai, va dau, bi dau

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 ky ((mang may) or (nang cao)) hoi. thien van nam ((duc ban) OR (duc tan)) thanh vi dau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky ((mang may) OR (nang cao)) hoi. thien van nam ((duc ban) OR (duc tan)) thanh vi dau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky ((mang may) or (nang cao)) hoi. thien van nam ((duc ban) OR (duc tan)) thanh vi dau tren".
• Adding a wildcard symbol may retrieve word variants: tu sach ky ((mang may) or (nang cao)) hoi. thien van nam ((duc ban) OR (duc tan)) thanh vi dau tren*.