Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
trinh vat » trinh van, trinh luat, sinh vat
thu sach » tu sach, thuat sach, thuoc sach
xuan hoi » xuan loi, xuan hoa, quang hoi
xuan ho » xuan ha, xuan huy, xuan thu
sach ky » sac ky, sach y, sach ty
bach he » bach hue, bach ha, bach nhu
chu tre » cho tre, chu tri, cuu tre
he va » che va, he van, te va

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu sach ky nang ((xuan hoi) OR (xuan ho)). hieu vien bach he va ((trinh vat) or (tich va)) chu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ky nang ((xuan hoi) OR (xuan ho)). hieu vien bach he va ((trinh vat) OR (tich va)) chu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach ky nang ((xuan hoi) OR (xuan ho)). hieu vien bach he va ((trinh vat) or (tich va)) chu tre".
• Adding a wildcard symbol may retrieve word variants: thu sach ky nang ((xuan hoi) OR (xuan ho)). hieu vien bach he va ((trinh vat) or (tich va)) chu tre*.