Perhaps you should try some spelling variations:
trinh cao » trinh chao, trinh co, tinh cao
trinh cau » trinh chat, trinh chao, trinh tu
hoi viet » oi viet, thai viet, cuoi viet
hai viet » thai viet, mai viet, tai viet
cau luan » cu luan, dau luan, lau luan
cau giay » cuu giai, cac giai
hoc viet » hoc hien
cao van » cac van, dao van, cao dang
luan va » luan van, luat va
co hoi » co loi
ca cay » cua cay, cac cay, ca cac
van va » van vat, van van, ban va
cay co » cac co, tay co, cay cong
va ca » va cac, va cao, va cai
cay o » cay mo, cay ot, cay so
o hai » co hai, so hai, o lai

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( cong trinh cao van va ((cau xay) or (cau giay)) co hoi viet nam ) or ((( chuong trinh cau luan va ca cay o hai viet nam ) or ( chuong trinh cau luan va ca cay co hoc viet nam ))))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( cong trinh cao van va ((cau xay) OR (cau giay)) co hoi viet nam ) OR ((( chuong trinh cau luan va ca cay o hai viet nam ) OR ( chuong trinh cau luan va ca cay co hoc viet nam )))).
• Adding a wildcard symbol may retrieve word variants: (( cong trinh cao van va ((cau xay) or (cau giay)) co hoi viet nam ) or ((( chuong trinh cau luan va ca cay o hai viet nam ) or ( chuong trinh cau luan va ca cay co hoc viet nam ))))*.