Perhaps you should try some spelling variations:
hanh tai » thanh tai, hang tai, han tai
va trien » va truyen, va tuyen, va tieng
nang ma » tang ma, sang ma, nang cao
hieu va » lieu va, hieu qua
truc va » thuc va, thuc vat, trung va
va hanh » van hanh, va thanh, va danh
sai ky » sac ky
ma hoi » mai hoi, xa hoi, ma hoa
va cau » van cau, va cac, va dau
thiet » thieu

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 y) or (sai ky)) nang ma hoi. hieu va cau truc va hanh tai ((va trien) OR (va thiet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach y) OR (sai ky)) nang ma hoi. hieu va cau truc va hanh tai ((va trien) OR (va thiet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach y) or (sai ky)) nang ma hoi. hieu va cau truc va hanh tai ((va trien) OR (va thiet))".
• Adding a wildcard symbol may retrieve word variants: tu ((sach y) or (sai ky)) nang ma hoi. hieu va cau truc va hanh tai ((va trien) OR (va thiet))*.