Perhaps you should try some spelling variations:
vat hanh » vat thanh, van hanh, va hanh
pham duy » pham duc
hieu ve » hieu va, hieu van
vai cua » hai cua, lai cua, bai cua
ve pham » vi pham, v pham, ve phan
tu sach » thu sach, su sach, te sach
sach ty » sach y, sach tu, sach thu
tang ma » mang may, tang van
nang ma » sang ma, nang cao, mang may

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