Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
sach ty » sach y, sach tu, sach thu
vai cua » dai cua, hai cua, lai cua
va hanh » van hanh, va thanh, va danh
cac dac » cac dan, cac dai, cac bac
tu sach » thu sach, su sach, te sach
cac duc » cac du, cao duc, cac nuoc
cao hoi » cau hoi, co hoi, cao hoc
ty nang » ky nang, ty xang, ty hang
vi 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 ty nang cao hoi. hieu van ((cac duc) or (cac dac)) va hanh ((vi cua) OR (vai cua)) viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty nang cao hoi. hieu van ((cac duc) OR (cac dac)) va hanh ((vi cua) OR (vai cua)) viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ty nang cao hoi. hieu van ((cac duc) or (cac dac)) va hanh ((vi cua) OR (vai cua)) viet".
• Adding a wildcard symbol may retrieve word variants: tu sach ty nang cao hoi. hieu van ((cac duc) or (cac dac)) va hanh ((vi cua) OR (vai cua)) viet*.