Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
nam thuc » nam thuoc, am thuc, nam thu
ban hanh » ban hang
su triet » su viet, su tien, ve triet
nang mai » nang ma, nang tai, lang mai
thi lan » thi hanh, thi nang, thi lien
sach ky » sac ky, sach y, sach ty
mai hoi » mai khoi, dai hoi, lai hoi
van anh » van thanh, tuan anh, van minh
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 ky nang mai hoi. ((thi lan) or (ki nang)) nam thuc ((ban hanh) or (van anh)) di su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky nang mai hoi. ((thi lan) OR (ki nang)) nam thuc ((ban hanh) OR (van anh)) di su triet.
• Adding a wildcard symbol may retrieve word variants: toc sach ky nang mai hoi. ((thi lan) or (ki nang)) nam thuc ((ban hanh) or (van anh)) di su triet*.