Perhaps you should try some spelling variations:
pham thuc » pham chuc, nham thuc, pham thu
phap thuc » phap thu, phap hoc, phap tu
sach thu » sach thue, sach thieu, sach tham
hang hai » hoang hai, hang tai, thanh hai
sach thi » sach tai, sach thieu, sach tham
hai cua » thai cua, dai cua, hoi cua
nang ma » tang ma, sang ma, nang cao
va hang » van hang, va nang, va lang
hieu v » hieu va, hieu ve, hieu 2
ma hoi » mai hoi, xa hoi, ma hoa
cua te » cua tu

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

• Performing a fuzzy search may retrieve terms with similar spellings: so ((sach thi) OR (sach thu)) nang ma hoi. hieu v ((pham thuc) or (phap thuc)) va hang hai cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so ((sach thi) OR (sach thu)) nang ma hoi. hieu v ((pham thuc) OR (phap thuc)) va hang hai cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so ((sach thi) OR (sach thu)) nang ma hoi. hieu v ((pham thuc) or (phap thuc)) va hang hai cua te".
• Adding a wildcard symbol may retrieve word variants: so ((sach thi) OR (sach thu)) nang ma hoi. hieu v ((pham thuc) or (phap thuc)) va hang hai cua te*.