Perhaps you should try some spelling variations:
thien hach » thien thanh, hien hanh
hieu cach » hieu cac, chieu sach, hieu ca
trung vat » trung va, trong vat, truong van
trung van » truong van, trong van, trung va
dung cong » dung trong
cong bang » cuong bang, dong bang, hong bang
bang phan » nang phan, bang nhan, bang thanh
phan cau » phan dau, phan cac, phan tu

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

• Performing a fuzzy search may retrieve terms with similar spellings: hoc ((thien hach) or (hieu cach)) - thanh ((trung vat) OR (trung van)) dung cong bang phan cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc ((thien hach) OR (hieu cach)) - thanh ((trung vat) OR (trung van)) dung cong bang phan cau.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc ((thien hach) or (hieu cach)) - thanh ((trung vat) OR (trung van)) dung cong bang phan cau".
• Adding a wildcard symbol may retrieve word variants: hoc ((thien hach) or (hieu cach)) - thanh ((trung vat) OR (trung van)) dung cong bang phan cau*.