Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
hieu van » hieu va, thien van, lieu va
sach ty » sach y, sach tu, sach thu
vai cua » dai cua, hai cua, lai cua
van cac » van hac, van cau, van bac
te sach » toc sach
ty nang » ky nang, ty xang, ty hang
so hai » son hai, su hai, so ha
cac vo » cac co, cac vi, cac bo
vi cua » di cua
o hai » co hai, o lai, _ hai

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

• Performing a fuzzy search may retrieve terms with similar spellings: te sach ty nang ((o hai) OR (so hai)). hieu van cac vo van hanh ((vi cua) or (vai cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ty nang ((o hai) OR (so hai)). hieu van cac vo van hanh ((vi cua) OR (vai cua)) tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ty nang ((o hai) OR (so hai)). hieu van cac vo van hanh ((vi cua) or (vai cua)) tre".
• Adding a wildcard symbol may retrieve word variants: te sach ty nang ((o hai) OR (so hai)). hieu van cac vo van hanh ((vi cua) or (vai cua)) tre*.