Perhaps you should try some spelling variations:
trinh co » trinh do, trinh cong, trinh hoa
cho tang » cao tang, kho tang, cho hang
cay cong » cac cong, cao cong, cau cong
hoi viet » hai viet, oi viet, thai viet
cong hoi » cong nhoi, cong hoa, cong hai
cac cay » ca cay, cac cam, cac cap
co tang » cao tang, ca tang, do tang
co dang » cao dang, co dan, co dong
dang va » dang van, dang vat, hang va
cao lan » cao van, cao dang, cao tang
cay co » cac co, tay co
co hoi » co hoc, co loi
co lan » co ban, co dan, co lao

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 ((co tang) OR (cho tang)) va cac cay co hoi viet nam ) or ( cong trinh co dang va cac cay co hoi viet nam ))) or ( cong trinh ((co lan) or (cao lan)) va cac cay cong hoi viet nam ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((( cong trinh ((co tang) OR (cho tang)) va cac cay co hoi viet nam ) OR ( cong trinh co dang va cac cay co hoi viet nam ))) OR ( cong trinh ((co lan) OR (cao lan)) va cac cay cong hoi viet nam )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(((( cong trinh ((co tang) OR (cho tang)) va cac cay co hoi viet nam ) or ( cong trinh co dang va cac cay co hoi viet nam ))) or ( cong trinh ((co lan) or (cao lan)) va cac cay cong hoi viet nam ))".
• Adding a wildcard symbol may retrieve word variants: (((( cong trinh ((co tang) OR (cho tang)) va cac cay co hoi viet nam ) or ( cong trinh co dang va cac cay co hoi viet nam ))) or ( cong trinh ((co lan) or (cao lan)) va cac cay cong hoi viet nam ))*.