Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
kho tang » cao tang
vai cua » hai cua, lai cua, bai cua
xa hanh » xa thanh, xa khanh, va hanh
cam tuc » cam xuc, cam tu, nam thuc
van cam » van nam, van lam, van cau
tu sach » thu sach, su sach, te sach
ky tang » ky nang, ky dang, ky trong
ma hoi » mai hoi, xa hoi, ma hoa

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 ((ky tang) OR (kho tang)) ma hoi. hieu van cam tuc xa hanh ((vai cua) or (dai cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((ky tang) OR (kho tang)) ma hoi. hieu van cam tuc xa hanh ((vai cua) OR (dai cua)) tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((ky tang) OR (kho tang)) ma hoi. hieu van cam tuc xa hanh ((vai cua) or (dai cua)) tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ((ky tang) OR (kho tang)) ma hoi. hieu van cam tuc xa hanh ((vai cua) or (dai cua)) tre*.