Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
hang hai » hoang hai, hang tai, thanh hai
vien cac » vien bach, vien dai, vien da
su sach » so sach, vu sach
duc van » duc va, duc tan, duc manh
duc ban » duc tan, dua ban, duc man
cua tre » cua te, cuu tre, cua triet
sach v » sach va, sach y, sach 2
v nang » va nang, vu nang, van nang
x hoi » xa hoi, o hoi, x ho

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach v nang x hoi. hieu vien cac ((duc ban) OR (duc van)) ((hang hai) or (hang va)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach v nang x hoi. hieu vien cac ((duc ban) OR (duc van)) ((hang hai) OR (hang va)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach v nang x hoi. hieu vien cac ((duc ban) OR (duc van)) ((hang hai) or (hang va)) cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach v nang x hoi. hieu vien cac ((duc ban) OR (duc van)) ((hang hai) or (hang va)) cua tre*.