Perhaps you should try some spelling variations:
thanh mai » thanh hai, thanh tai, thanh moi
sang mai » sang ma, sang tai, lang mai
va trien » va truyen, va tuyen, va tieng
hieu van » hieu va, thien van, lieu va
su sach » so sach, vu sach
truc va » thuc va, thuc vat, trung va
sach ky » sac ky, sach y, sach ty
van cam » van nam, van lam, van cau
mai hoi » mai khoi, dai hoi, lai hoi
ky sang » ky nang, ky dang, ky tang
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: su sach ky sang mai hoi. hieu van cam ((duc va) or (truc va)) thanh mai ((va trien) OR (va thiet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky sang mai hoi. hieu van cam ((duc va) OR (truc va)) thanh mai ((va trien) OR (va thiet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky sang mai hoi. hieu van cam ((duc va) or (truc va)) thanh mai ((va trien) OR (va thiet))".
• Adding a wildcard symbol may retrieve word variants: su sach ky sang mai hoi. hieu van cam ((duc va) or (truc va)) thanh mai ((va trien) OR (va thiet))*.