Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
vien cac » vien bach, vien dai, vien da
hang hai » hoang hai, hang tai, thanh hai
duc ban » duc tan, duc van, dua ban
cac duc » cac du, cao duc, cac dac
cua tre » cua te, cuu tre, cua triet
sach v » sach va, sach y, sach vay
sach 2 » sach y
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) OR (sach 2)) nang x hoi. hieu vien cac duc ban ((hang hai) or (hang va)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach v) OR (sach 2)) nang x hoi. hieu vien cac duc ban ((hang hai) OR (hang va)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach v) OR (sach 2)) nang x hoi. hieu vien cac duc ban ((hang hai) or (hang va)) cua tre".
• Adding a wildcard symbol may retrieve word variants: su ((sach v) OR (sach 2)) nang x hoi. hieu vien cac duc ban ((hang hai) or (hang va)) cua tre*.