Perhaps you should try some spelling variations:
toc sach » doc sach, thuoc sach, nuoc sach
nam thuc » nam thuoc, am thuc, nam thu
hoc sach » hoc sinh, hoc cac, hoc anh
ban hanh » ban hang
lang mai » lang dai, lang hai, lang man
van anh » van thanh, tuan anh, van minh
thi van » thi lan, thi hanh, thi nang
mai hoi » mai khoi, dai hoi, lai hoi
ky lang » ky nang, ky dang, ky tang
su tien » su kien, su hien, tu tieng
di su » doi su, ki su, da su

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((toc sach) OR (hoc sach)) ky lang mai hoi. thi van nam thuc ((ban hanh) or (van anh)) di su tien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (hoc sach)) ky lang mai hoi. thi van nam thuc ((ban hanh) OR (van anh)) di su tien.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) OR (hoc sach)) ky lang mai hoi. thi van nam thuc ((ban hanh) or (van anh)) di su tien".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) OR (hoc sach)) ky lang mai hoi. thi van nam thuc ((ban hanh) or (van anh)) di su tien*.