Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
hanh vai » hanh vi, hanh va, hanh tai
su triet » su viet, su tien, ve triet
ve phan » va phan, ke phan, ve phat
thuc va » thuc vat, thuc dan, thuc day
va hanh » van hanh, va thanh, va danh
ty nang » ky nang, ty hang, ly nang
ve pham » vi pham, v pham, ve phat
vai su » va su, van su, lai su

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

• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach ((ty nang) OR (ty xang)) ma hoa. hieu ((ve pham) OR (ve phan)) thuc va hanh vai su triet~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc sach ((ty nang) or (ty xang)) ma hoa. hieu ((ve pham) OR (ve phan)) thuc va hanh vai su triet~".
• Adding a wildcard symbol may retrieve word variants: doc sach ((ty nang) or (ty xang)) ma hoa. hieu ((ve pham) OR (ve phan)) thuc va hanh vai su triet*.