Perhaps you should try some spelling variations:
thanh dai » thanh hai, thanh tai, thanh dat
dang xay » dang van, van xay
va thanh » gia thanh, ban thanh, va tinh
nang ma » tang ma, sang ma, nang cao
hieu va » lieu va, hieu qua
cac hoc » cach hoc, cac hop, bac hoc
sac ky » sai ky
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: te ((sac ky) OR (cac ky)) ((nang ma) or (dang xay)) hoi. hieu va cac hoc va thanh dai cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te ((sac ky) OR (cac ky)) ((nang ma) OR (dang xay)) hoi. hieu va cac hoc va thanh dai cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te ((sac ky) OR (cac ky)) ((nang ma) or (dang xay)) hoi. hieu va cac hoc va thanh dai cua te".
• Adding a wildcard symbol may retrieve word variants: te ((sac ky) OR (cac ky)) ((nang ma) or (dang xay)) hoi. hieu va cac hoc va thanh dai cua te*.