Perhaps you should try some spelling variations:
thanh hai » thanh phan, thanh hoa, thanh san
hanh hai » nhanh hai, hang hai, hanh tai
hieu van » hieu va, thien van, lieu va
van tuan » van quan, van ban, anh tuan
cao hoi » cau hoi, co hoi, cao hoc
sach ty » sach y, sach thu, xach tay
sach tu » sach thu, cach tu, sach uu
tuan du » toan du, xuan du, tuan cu
cua tre » cua te, cuu tre, cua triet
du va » dau va, tu va, su va

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

• Performing a fuzzy search may retrieve terms with similar spellings: hoc ((sach tu) OR (sach ty)) nang cao hoi. hieu van tuan du va ((hanh hai) or (thanh hai)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc ((sach tu) OR (sach ty)) nang cao hoi. hieu van tuan du va ((hanh hai) OR (thanh hai)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc ((sach tu) OR (sach ty)) nang cao hoi. hieu van tuan du va ((hanh hai) or (thanh hai)) cua tre".
• Adding a wildcard symbol may retrieve word variants: hoc ((sach tu) OR (sach ty)) nang cao hoi. hieu van tuan du va ((hanh hai) or (thanh hai)) cua tre*.