Perhaps you should try some spelling variations:
thuc dan » thuc hanh, hoc dan, thuc vat
hieu van » hieu va, thien van, lieu va
van chat » cao chat
vai cua » dai cua, hai cua, lai cua
don vai » don vi, don va, den vai
nang xa » nang x, lang xa, mang xa
thuc va » thuc vat, thuc day
nang ma » tang ma, sang ma, nang cao
cua tre » cua te, cuu tre, cua triet

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu cac ky ((nang xa) or (nang ma)) hoi. hieu van chat ((thuc va) OR (thuc dan)) don vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu cac ky ((nang xa) OR (nang ma)) hoi. hieu van chat ((thuc va) OR (thuc dan)) don vai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu cac ky ((nang xa) or (nang ma)) hoi. hieu van chat ((thuc va) OR (thuc dan)) don vai cua tre".
• Adding a wildcard symbol may retrieve word variants: tu cac ky ((nang xa) or (nang ma)) hoi. hieu van chat ((thuc va) OR (thuc dan)) don vai cua tre*.