Perhaps you should try some spelling variations:
tinh dan » trinh dan, tinh da, binh dan
duoc may » duoc ma, duoc ly, hoc may
nam duoc » nam thuoc, da duoc, dat duoc
hieu van » hieu va, thien van, lieu va
sach ky » sac ky, sach ty, sach kem
sang ma » tang ma, sang tao, mang may
cu tren » tu tren, dua tren
nang ma » tang ma, nang cao, mang may
dan cu » dan cua, dan ca, dan su

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