Perhaps you should try some spelling variations:
ve triet » va trien, su triet
hanh dao » lanh dao, thanh dat, thanh dam
thuc dan » thuc hanh, hoc dan, thuc vat
su sach » so sach, vu sach
hieu ve » hieu va, hieu van
mai hoi » mai khoi, dai hoi, lai hoi
ky tang » ky nang, ky dang, kho tang
ky sang » ky nang, ky dang, duy sang
ve cham » va cham, ve chat, vu cham
tuc va » thuc va, truc va, tuc xa
dao ve » bao ve, dap ve, dau ve

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