Perhaps you should try some spelling variations:
nham thuc » nhan thuc, nam thuc, nham thu
thuc van » thuc vat, thuc dan, thuc va
van hanh » van thanh, ban hanh, van anh
su triet » su viet, su tien, ve triet
tu sach » thu sach, su sach, te sach
sach vu » sach va, sach tu, sach uu
mai hoi » mai khoi, dai hoi, lai hoi
hieu va » lieu va, hieu qua
va nham » va cham, va tham, va nha
hanh ki » hanh vi, hanh ky, hanh kien
ma hoi » xa hoi, ma hoa, me hoi
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 vu quang ((ma hoi) or (mai hoi)). hieu va nham thuc van hanh ki su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach vu quang ((ma hoi) OR (mai hoi)). hieu va nham thuc van hanh ki su triet.
• Adding a wildcard symbol may retrieve word variants: tu sach vu quang ((ma hoi) or (mai hoi)). hieu va nham thuc van hanh ki su triet*.