Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
tu sach » thu sach, su sach, te sach
nang xa » nang x, lang xa, nang ma
dau xua » dao xuan, dau luan, dac xuan
dau cua » dai cua, day cua, cau cua
cua tre » cua te, cuu tre, cua triet
y nang » ky nang, ly nang, v nang
vi cua » vai cua, di cua

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 hoach)) y nang xa hoi. hieu qua ((dau xua) OR (dau cua)) van hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (thu hoach)) y nang xa hoi. hieu qua ((dau xua) OR (dau cua)) van hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (thu hoach)) y nang xa hoi. hieu qua ((dau xua) OR (dau cua)) van hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (thu hoach)) y nang xa hoi. hieu qua ((dau xua) OR (dau cua)) van hanh vi cua tre*.