Perhaps you should try some spelling variations:
ban thanh » ban hanh, ban hang
van thanh » van tuan
thu sach » tu sach, thuat sach, thuoc sach
sang mai » sang ma, sang tai, lang mai
mai khoi » mai khoa, tai khoa, cac khoi
la tren » loai tren, dua tren, dat tren
sach ky » sac ky, sach y, sach ty
ky sang » ky nang, ky dang, ky tang
ve cac » va cac, vien cac
ve cau » ke cau, va cau, le cau
vai la » tai la, vai va

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu sach ky sang mai khoi. hieu ((ve cau) or (ve cac)) luc ((van thanh) OR (ban thanh)) vai la tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ky sang mai khoi. hieu ((ve cau) OR (ve cac)) luc ((van thanh) OR (ban thanh)) vai la tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach ky sang mai khoi. hieu ((ve cau) or (ve cac)) luc ((van thanh) OR (ban thanh)) vai la tren".
• Adding a wildcard symbol may retrieve word variants: thu sach ky sang mai khoi. hieu ((ve cau) or (ve cac)) luc ((van thanh) OR (ban thanh)) vai la tren*.