Perhaps you should try some spelling variations:
vien cac » vien bach, vien dai, vien da
su sach » so sach, vu sach
xa nong » xa dong, xuat nong, may nong
ky lang » ky nang, ky dang, ky tang
lang ha » long ha
da nang » cam nang, kha nang, cao nang
sach ky » sac ky, sach y, sach ty
ve cac » va cac
ha hoi » hoa hoi, ha noi, xa hoi
doi va » hoi va, noi va, dai va
thiet » thieu

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach ky lang ha hoi. hieu ((ve cac) OR (vien cac)) toc ((xa nong) or (da nang)) doi va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky lang ha hoi. hieu ((ve cac) OR (vien cac)) toc ((xa nong) OR (da nang)) doi va thiet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky lang ha hoi. hieu ((ve cac) OR (vien cac)) toc ((xa nong) or (da nang)) doi va thiet".
• Adding a wildcard symbol may retrieve word variants: su sach ky lang ha hoi. hieu ((ve cac) OR (vien cac)) toc ((xa nong) or (da nang)) doi va thiet*.