Perhaps you should try some spelling variations:
tham thuc » nham thuc, pham thuc, tam thuc
hieu van » hieu va, thien van, lieu va
van tham » van thanh, van tuan, van chat
va thieu » va thiet, va hieu, va tieu
tu sach » thu sach, su sach, te sach
ky lang » ky dang, ky tang, tay lang
va hanh » van hanh, va thanh, va danh
va han » va phan, van han, va hang

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 lang) or (ky nang)) xa hoi. hieu van tham thuc ((va han) or (va hanh)) tri va thieu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((ky lang) OR (ky nang)) xa hoi. hieu van tham thuc ((va han) OR (va hanh)) tri va thieu.
• Adding a wildcard symbol may retrieve word variants: tu sach ((ky lang) or (ky nang)) xa hoi. hieu van tham thuc ((va han) or (va hanh)) tri va thieu*.