Perhaps you should try some spelling variations:
pham thuc » phap thuc, pham chuc, nham thuc
tham thuc » nham thuc, tam thuc, thai thuc
hanh vii » hanh voi, hanh va, hanh noi
tu sach » thu sach, su sach, te sach
sach ty » sach y, sach tu, sach thu
cu tren » tu tren, dua tren
hieu ve » hieu va, hieu van
mai hoi » mai khoi, dai hoi, lai hoi
anh mai » anh bai, anh mau, anh ma
ty anh » ly anh, thuy anh

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 anh mai hoi. hieu ve ((tham thuc) or (pham thuc)) va ((hanh vii) or (hanh vi)) cu tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty anh mai hoi. hieu ve ((tham thuc) OR (pham thuc)) va ((hanh vii) OR (hanh vi)) cu tren.
• Adding a wildcard symbol may retrieve word variants: tu sach ty anh mai hoi. hieu ve ((tham thuc) or (pham thuc)) va ((hanh vii) or (hanh vi)) cu tren*.