Perhaps you should try some spelling variations:
phan duc » pham duc, phan tu, phan dau
tu sach » thu sach, su sach, te sach
sach ty » sach y, sach tu, sach thu
ty nang » ky nang, ty xang, ty hang
dau hoi » cau hoi, dan hoi, dau noi
dai hoi » dai hoc, dai hai, dai moi
hieu ve » hieu va, hieu van
ve phan » va phan, ke phan, ve phat
va dinh » van dinh, va kinh, va tinh
dinh di » dinh du, dinh vi, danh di
cua tre » cua te, cuu tre, cua triet
di cua » dai cua, doi cua, de 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 ty nang ((dau hoi) or (dai hoi)). hieu ve phan duc va dinh di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty nang ((dau hoi) OR (dai hoi)). hieu ve phan duc va dinh di cua tre.
• Adding a wildcard symbol may retrieve word variants: tu sach ty nang ((dau hoi) or (dai hoi)). hieu ve phan duc va dinh di cua tre*.