Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
dau tren » dau tien, dat tren, dau tieng
tu sach » thu sach, su sach, te sach
hieu ve » hieu va, hieu van
cam duc » cam xuc, cao duc, pham duc
va hanh » va thanh, va danh, ban hanh
cua tre » cua te, cuu tre, cua triet
y nang » ky nang, ly nang, v nang
nang o » nang co, nang ho, nang ro
ve cam » ve cham, ve cac, va cam
o hoi » co hoi, o hoc, o hai

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