Perhaps you should try some spelling variations:
hac truc » hoc truc, hang truc, sach truc
nang mai » nang ma, nang tai, lang mai
van hanh » van thanh, ban hanh, van ban
hai cua » thai cua, dai cua, hoi cua
van anh » van thanh, tuan anh, van minh
cua tre » cua te, cuu tre, cua triet
sach ky » sach y, sach ty, sach kem
hieu va » lieu va, hieu qua
mai hoi » mai khoi, dai hoi, lai hoi
sac ky » cac ky, sai ky
va hac » van hac, va khac, va cac

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: vu ((sach ky) OR (sac ky)) nang mai hoi. hieu va hac truc ((van hanh) OR (van anh)) hai cua tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "vu ((sach ky) or (sac ky)) nang mai hoi. hieu va hac truc ((van hanh) OR (van anh)) hai cua tre~".
• Adding a wildcard symbol may retrieve word variants: vu ((sach ky) or (sac ky)) nang mai hoi. hieu va hac truc ((van hanh) OR (van anh)) hai cua tre*.