Perhaps you should try some spelling variations:
trinh cao » trinh chao, trinh cau, tinh cao
thai viet » thi viet, tai viet, mai viet
trinh co » trinh cong, trinh hoa, trinh ky
loi viet » loai viet, hoi viet, oi viet
hoc viet » hoc hien
trinh do » trinh ky
doi viet » dai viet, hoi viet, oi viet
bao tap » bai tap, ba tap, bao tay
cac tac » cac toc, cac bac, cac dac
cao lan » cao van, cao dang, cao tang
co lanh » co anh, co hanh, cay lanh
dao cay » dao tay, dau cay, tao cay
lanh va » hanh va, anh va, lanh dao
do thai » do thi, toc thai
cao tai » cao tang
co loi » co hoi
cay co » cac co, tay co, cay cong
co doi » cho doi, co dot, co dai
tac co » tuc co, cac co, toc co
lan va » luan va, lan van, lang va
va cao » va co
tai co » mai co, tai so, tri co
do dan » do danh, dao dan, do dang
va bao » va bai
cay do » cau do, cap do, cay mo
ca dan » cac dan
co dan » co ban, cao dang

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

• If you are trying to use Boolean operators, they must be ALL CAPS: (((((( cong trinh co lanh va cao tai co loi viet nam ) OR ( cong trinh co lanh va bao tap co loi viet nam ))) OR ((( cong trinh ((co dan) OR (ca dan)) va dao cay do thai viet nam ) OR ( cong trinh do dan ca dao cay co hoc viet nam ))))) OR ( cong trinh cao lan va cac tac co doi viet nam ))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(((((( cong trinh co lanh va cao tai co loi viet nam ) or ( cong trinh co lanh va bao tap co loi viet nam ))) or ((( cong trinh ((co dan) OR (ca dan)) va dao cay do thai viet nam ) or ( cong trinh do dan ca dao cay co hoc viet nam ))))) or ( cong trinh cao lan va cac tac co doi viet nam ))~".
• Adding a wildcard symbol may retrieve word variants: (((((( cong trinh co lanh va cao tai co loi viet nam ) or ( cong trinh co lanh va bao tap co loi viet nam ))) or ((( cong trinh ((co dan) OR (ca dan)) va dao cay do thai viet nam ) or ( cong trinh do dan ca dao cay co hoc viet nam ))))) or ( cong trinh cao lan va cac tac co doi viet nam ))*.