Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
duoc may » duoc ma, duoc ly, hoc may
nam duoc » nam thuoc, da duoc, dat duoc
nang ma » tang ma, sang ma, nang cao
sach ky » sac ky, sach y, sach kem
sach ty » sach y, sach tu, sach thu
ma hoi » mai hoi, xa hoi, ma hoa
da ca » da cau, da cua, va ca

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

• Performing a fuzzy search may retrieve terms with similar spellings: thuat ((sach ky) OR (sach ty)) nang ma hoi. hieu van nam duoc may tinh ((da ca) or (dan ca)) tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thuat ((sach ky) OR (sach ty)) nang ma hoi. hieu van nam duoc may tinh ((da ca) OR (dan ca)) tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thuat ((sach ky) OR (sach ty)) nang ma hoi. hieu van nam duoc may tinh ((da ca) or (dan ca)) tren".
• Adding a wildcard symbol may retrieve word variants: thuat ((sach ky) OR (sach ty)) nang ma hoi. hieu van nam duoc may tinh ((da ca) or (dan ca)) tren*.