Perhaps you should try some spelling variations:
tu sach » thu sach, su sach, te sach
sach ty » sach y, sach tu, sach thu
ty nang » ky nang, ty xang, ty hang
hieu va » lieu va, hieu qua
va pham » van pham, va phat, va phap
va danh » va dinh, va dan, va hanh
vai cua » dai cua, hai cua, lai cua
vi cua » di cua
x hoi » o hoi, x ho, 5 hoi

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

• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty nang ((x hoi) OR (xa hoi)). hieu va pham duc va danh ((vi cua) OR (vai cua)) tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ty nang ((x hoi) OR (xa hoi)). hieu va pham duc va danh ((vi cua) or (vai cua)) tre~".
• Adding a wildcard symbol may retrieve word variants: tu sach ty nang ((x hoi) OR (xa hoi)). hieu va pham duc va danh ((vi cua) or (vai cua)) tre*.