Perhaps you should try some spelling variations:
thanh mai » thanh hai, thanh tai, thanh moi
va trien » va truyen, va thiet, va tuyen
sang mai » sang ma, sang tai, lang mai
hieu van » hieu va, thien van, lieu va
ky sang » ky nang, ky dang, ky tang
mai hoi » mai khoi, dai hoi, lai hoi
van cam » van nam, van lam, van cau
truc va » thuc va, thuc vat, trung va
vu sach » vu bach, vu khach
su sach » so sach

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: ((su sach) OR (vu sach)) ky sang mai hoi. hieu van cam ((duc va) or (truc va)) thanh mai va trien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sach) OR (vu sach)) ky sang mai hoi. hieu van cam ((duc va) OR (truc va)) thanh mai va trien.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((su sach) OR (vu sach)) ky sang mai hoi. hieu van cam ((duc va) or (truc va)) thanh mai va trien".
• Adding a wildcard symbol may retrieve word variants: ((su sach) OR (vu sach)) ky sang mai hoi. hieu van cam ((duc va) or (truc va)) thanh mai va trien*.