Perhaps you should try some spelling variations:
thien san » thien van, trien san, thien ban
pham thuc » phap thuc, pham chuc, nham thuc
thu sach » thuat sach, thuoc sach, thu hoach
tu sach » su sach, te sach, tu cach
cao hoi » cau hoi, co hoi, tao hoi
cao hoc » co hoc, cho hoc, chat hoc
thuc va » thuc vat, thuc dan, thuc day
dan mai » doan mai, ban mai, dan tai
va dan » ca dan, va dao, 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) or (thu sach)) ky nang ((cao hoi) or (cao hoc)). thien san pham thuc va dan mai va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (thu sach)) ky nang ((cao hoi) OR (cao hoc)). thien san pham thuc va dan mai va thiet.
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (thu sach)) ky nang ((cao hoi) or (cao hoc)). thien san pham thuc va dan mai va thiet*.