Perhaps you should try some spelling variations:
sang mai » sang ma, sang tai, lang mai
thuc dan » thuc hanh, hoc dan, thuc vat
sach ky » sac ky, sach y, sach ty
su sach » so sach, vu sach
ve cham » va cham, ve chat, vu cham
hieu ve » hieu va, hieu van
mai hoi » mai khoi, dai hoi, lai hoi
ky sang » ky nang, ky dang, ky tang
dao ve » dap ve, dau ve, dao viet
tuc va » thuc va, truc va, tuc xa

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 sang mai hoi. hieu ve cham ((tuc va) or (thuc dan)) hanh ((dao ve) OR (bao ve)) triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky sang mai hoi. hieu ve cham ((tuc va) OR (thuc dan)) hanh ((dao ve) OR (bao ve)) triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky sang mai hoi. hieu ve cham ((tuc va) or (thuc dan)) hanh ((dao ve) OR (bao ve)) triet".
• Adding a wildcard symbol may retrieve word variants: su sach ky sang mai hoi. hieu ve cham ((tuc va) or (thuc dan)) hanh ((dao ve) OR (bao ve)) triet*.