Perhaps you should try some spelling variations:
trinh chao » trinh chat, trinh co, trinh giao
trinh han » trinh quan
dai viet » mai viet, dao viet, tai viet
doi viet » oi viet, do viet, doc viet
chao lan » cao lan, chao van, chao yang
hoi viet » hai viet, oi viet, thai viet
co thai » do thai, ca thai, co hai
han lan » phan lan, han luan, han san
cac tay » cac tac, cac tai, cac tap
cac cay » ca cay, cac cam, cac cau
cac cap » cao cap, cac cam, cac cau
co thi » cao thi, do thi, vo thi
cap co » cap cho, tap co, cap do
lan va » luan va, lanh va, lan van
cay co » cac co, tay co, cay cong
co hoi » co hoc, co loi

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 chao lan va cac tay ((co thi) or (co thai)) viet nam ) or ((( cong trinh han lan va cac cap co ((doi viet) or (dai viet)) nam ) or ( cong trinh chao lan va cac cay co hoi viet nam ))))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( cong trinh chao lan va cac tay ((co thi) OR (co thai)) viet nam ) OR ((( cong trinh han lan va cac cap co ((doi viet) OR (dai viet)) nam ) OR ( cong trinh chao lan va cac cay co hoi viet nam )))).
• Adding a wildcard symbol may retrieve word variants: (( cong trinh chao lan va cac tay ((co thi) or (co thai)) viet nam ) or ((( cong trinh han lan va cac cap co ((doi viet) or (dai viet)) nam ) or ( cong trinh chao lan va cac cay co hoi viet nam ))))*.