Perhaps you should try some spelling variations:
cach hoc » cach thuc, cach thoi, dich hoc
van hanh » van thanh, ban hanh, van anh
dang tay » dang xay, dung tay, dan tay
cua tre » cua te, cuu tre, cua triet
va dinh » van dinh, va kinh, va tinh
va cach » va cac
hieu va » lieu va, hieu qua
tay hoi » tay ho, tao hoi, tay thai
sac ky » sai ky

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu ((sac ky) or (cac ky)) dang tay hoi. hieu va cach hoc ((van hanh) or (va dinh)) dai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sac ky) OR (cac ky)) dang tay hoi. hieu va cach hoc ((van hanh) OR (va dinh)) dai cua tre.
• Adding a wildcard symbol may retrieve word variants: tu ((sac ky) or (cac ky)) dang tay hoi. hieu va cach hoc ((van hanh) or (va dinh)) dai cua tre*.