Perhaps you should try some spelling variations:
thanh va » thanh van, hanh va, thanh ha
su sach » so sach, vu sach
thue va » thuc va, thuyet va, thuc vat
sach ky » sac ky, sach y, sach ty
tang ma » mang may, tang van
hieu ve » hieu va, hieu van
cua tre » cua te, cuu tre, cua triet
ve cam » ve cham, ve cac, va cam
thu va » thuc va, tu va, thu ha
va cua » va chua, via cua, ca cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach ky ((nang x) or (tang ma)) hoi. hieu ve cam ((thu va) OR (thue va)) thanh va cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky ((nang x) OR (tang ma)) hoi. hieu ve cam ((thu va) OR (thue va)) thanh va cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky ((nang x) or (tang ma)) hoi. hieu ve cam ((thu va) OR (thue va)) thanh va cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach ky ((nang x) or (tang ma)) hoi. hieu ve cam ((thu va) OR (thue va)) thanh va cua tre*.