Perhaps you should try some spelling variations:
nam thuoc » nam thuc, nam thu, nha thuoc
cua triet » cua viet, su triet
va triet » va thiet, va trien, ve triet
hanh tai » thanh tai, hang tai, han tai
thuoc va » thuc va, thuoc ma, thuong va
va hanh » van hanh, va thanh, va danh
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
hieu va » lieu va, hieu qua
hoa hoi » khoa hoi, hoa doi, hoc hoi
ky lang » ky nang, ky dang, ky tang
va nam » van nam, ha nam, va nay

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