Perhaps you should try some spelling variations:
nam thuc » nam thuoc, am thuc, nam thu
manh vai » manh hai, manh va, manh khai
dan manh » dang manh, doan manh, van manh
thuc dan » thuc hanh, hoc dan, thuc vat
tu sach » thu sach, su sach, te sach
ca viet » va viet, hoa viet, san viet
co viet » so viet, o viet, hoc viet
sach ky » sac ky, sach y, sach ty
hieu va » lieu va, hieu qua
hieu ve » hieu van
x hoi » xa hoi, o hoi, x ho

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 nang x hoi. ((hieu ve) or (hieu va)) nam thuc dan manh vai ((ca viet) OR (co viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang x hoi. ((hieu ve) OR (hieu va)) nam thuc dan manh vai ((ca viet) OR (co viet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang x hoi. ((hieu ve) or (hieu va)) nam thuc dan manh vai ((ca viet) OR (co viet))".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang x hoi. ((hieu ve) or (hieu va)) nam thuc dan manh vai ((ca viet) OR (co viet))*.