Perhaps you should try some spelling variations:
hieu vien » hieu viec, thieu nien, hieu tieng
hieu hien » bieu hien, dieu hien, chieu chien
thu sach » thuat sach, thuoc sach, thu hoach
nang mai » nang ma, nang tai, lang mai
hanh hai » thanh hai, nhanh hai, hang hai
tu sach » su sach, te sach, tu cach
cac luc » cau luc, coc luc, cac nuoc
hai cua » thai cua, dai cua, hoi cua
mai hoi » mai khoi, dai hoi, lai hoi
va hanh » van hanh, va thanh, va danh
luc va » duc va, tuc va, loc va
cua te » cua tu

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((tu sach) or (thu sach)) ky nang mai hoi. ((hieu vien) OR (hieu hien)) cac luc va hanh hai cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (thu sach)) ky nang mai hoi. ((hieu vien) OR (hieu hien)) cac luc va hanh hai cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (thu sach)) ky nang mai hoi. ((hieu vien) OR (hieu hien)) cac luc va hanh hai cua te".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (thu sach)) ky nang mai hoi. ((hieu vien) OR (hieu hien)) cac luc va hanh hai cua te*.