Perhaps you should try some spelling variations:
hoc sach » hoc sinh, hoc anh
nang mai » nang ma, nang tai, lang mai
nam thuc » nam thuoc, am thuc, nam thu
hanh vai » hanh vi, hanh va, hanh tai
tu sach » thu sach, su sach, te sach
hoc cac » hoc cao
mai hoi » mai khoi, dai hoi, lai hoi
hieu va » lieu va, hieu qua
thuc va » thuc vat, thuc dan, thuc day
va hanh » van hanh, va thanh, va danh
vai cua » dai cua, hai cua, lai cua
va nam » van nam, ha nam, va nay
cua te » cua tu

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) or (((hoc sach) OR (hoc cac)))) ky nang mai hoi. hieu va nam thuc va hanh vai cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (((hoc sach) OR (hoc cac)))) ky nang mai hoi. hieu va nam thuc va hanh vai cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (((hoc sach) OR (hoc cac)))) ky nang mai hoi. hieu va nam thuc va hanh vai cua te".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (((hoc sach) OR (hoc cac)))) ky nang mai hoi. hieu va nam thuc va hanh vai cua te*.