Perhaps you should try some spelling variations:
nam thuc » nam thuoc, am thuc, nam thu
vat hanh » vat thanh, van hanh, va hanh
su triet » su tien, ve triet
tu sach » thu sach, su sach, te sach
ky lang » ky dang, ky tang, tay lang
hoa hoi » khoa hoi, hoa hoc, hoa doi
hieu ve » hieu va, hieu van
su viet » so viet
ve nam » he nam, va nam, le nam

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 lang) OR (ky nang)) hoa hoi. hieu ve nam thuc vat hanh vi ((su triet) or (su viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((ky lang) OR (ky nang)) hoa hoi. hieu ve nam thuc vat hanh vi ((su triet) OR (su viet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((ky lang) OR (ky nang)) hoa hoi. hieu ve nam thuc vat hanh vi ((su triet) or (su viet))".
• Adding a wildcard symbol may retrieve word variants: tu sach ((ky lang) OR (ky nang)) hoa hoi. hieu ve nam thuc vat hanh vi ((su triet) or (su viet))*.