Perhaps you should try some spelling variations:
cham hoc » chat hoc, cham hoi, cho hoc
toc sach » hoc sach, doc sach, thuoc sach
ban hanh » ban hang
nang mai » nang ma, nang tai, lang mai
hanh va » hang va, hanh vi
hieu va » lieu va, hieu qua
mai hoi » mai khoi, dai hoi, lai hoi
cua tre » cua te, cuu tre, cua triet
va cua » va chua, via cua, ca cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((te sach) or (toc sach)) ky nang mai hoi. hieu va ((cham hoc) OR (cham soc)) ban hanh va cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) ky nang mai hoi. hieu va ((cham hoc) OR (cham soc)) ban hanh va cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) or (toc sach)) ky nang mai hoi. hieu va ((cham hoc) OR (cham soc)) ban hanh va cua tre".
• Adding a wildcard symbol may retrieve word variants: ((te sach) or (toc sach)) ky nang mai hoi. hieu va ((cham hoc) OR (cham soc)) ban hanh va cua tre*.