Perhaps you should try some spelling variations:
may thoi » gay thoi, may thi, tay thoi
hanh dao » lanh dao, thanh dat, thanh dam
sach ky » sach y, sach ty, sach kem
va hanh » van hanh, va thanh, va danh
cac tuc » cac toc, cac tu, cac tac
hieu va » lieu va, hieu qua
may hoi » tay hoi, mai hoi, may hmi
su viet » so viet
sac ky » cac ky, sai ky
tuc va » thuc va, truc va, tuc xa
dao su » dao suu, dan su, cao su

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