Perhaps you should try some spelling variations:
sach tu » sach thu, sach ty, sach uu
hanh ki » hanh vi, hanh ky, hanh kien
luu van » cuu van, luan van, luu hanh
luc van » luoc van, duc van, luc va
va tham » van tham, va cham, va thanh
hieu va » lieu va, hieu qua
nang ma » tang ma, sang ma, nang cao
cach tu » cach thuc
su viet » so viet
ki su » ky su

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 tu) or (cach tu)) nang ma hoa. hieu va tham ((luc van) OR (luu van)) hanh ki su viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach tu) OR (cach tu)) nang ma hoa. hieu va tham ((luc van) OR (luu van)) hanh ki su viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach tu) or (cach tu)) nang ma hoa. hieu va tham ((luc van) OR (luu van)) hanh ki su viet".
• Adding a wildcard symbol may retrieve word variants: tu ((sach tu) or (cach tu)) nang ma hoa. hieu va tham ((luc van) OR (luu van)) hanh ki su viet*.