Perhaps you should try some spelling variations:
thieu nien » thien nhien
dieu hien » dieu khien, dieu kien, bieu hien
thu sach » thuat sach, thuoc sach, thu hoach
tu sach » su sach, te sach, tu cach
vai cua » dai cua, hai cua, lai cua
dan vai » dan va, dan tai, dan vat
cua dan » cua dang, cua ban, ca dan
bach tu » bach thu, cach tu, bac tu
cua tre » cua te, cuu tre, cua triet
tu cua » hu cua, vu cua
y nang » ky nang, ly nang, v 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: ((tu sach) OR (thu sach)) y nang x hoi. ((dieu hien) or (thieu nien)) bach tu cua dan vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (thu sach)) y nang x hoi. ((dieu hien) OR (thieu nien)) bach tu cua dan vai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) OR (thu sach)) y nang x hoi. ((dieu hien) or (thieu nien)) bach tu cua dan vai cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) OR (thu sach)) y nang x hoi. ((dieu hien) or (thieu nien)) bach tu cua dan vai cua tre*.