Perhaps you should try some spelling variations:
sieu viet » su viet, dien viet, bien viet
suu viet » su viet, sau viet, so viet
hanh dao » lanh dao, thanh dat, thanh dam
may thoi » gay thoi, may thi, tay thoi
sach ky » sac ky, sach y, sach ty
va hanh » van hanh, va thanh, va danh
tu sach » thu sach, su sach, te sach
hieu va » lieu va, hieu qua
may hoi » tay hoi, mai hoi, may hmi
ky mang » ky nang, ke mang, ky dang
cac tac » cac toc, cac bac, cac dac
tac va » tac da, tac xa, tuc va

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 mang ((may hoi) or (may thoi)). hieu va cac tac va hanh dao ((suu viet) OR (sieu viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky mang ((may hoi) OR (may thoi)). hieu va cac tac va hanh dao ((suu viet) OR (sieu viet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky mang ((may hoi) or (may thoi)). hieu va cac tac va hanh dao ((suu viet) OR (sieu viet))".
• Adding a wildcard symbol may retrieve word variants: tu sach ky mang ((may hoi) or (may thoi)). hieu va cac tac va hanh dao ((suu viet) OR (sieu viet))*.