Perhaps you should try some spelling variations:
thanh vai » thanh hai, thanh van, thanh tai
thuc dan » thuc hanh, hoc dan, thuc vat
hieu van » hieu va, thien van, lieu va
thuc va » thuc vat, thuc day
vai cua » dai cua, hai cua, lai cua
nang ma » tang ma, sang ma, nang cao
ma hoi » mai hoi, xa hoi, ma hoa
sac ky » cac 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: tu ((sach y) or (sac ky)) nang ma hoi. hieu van nam ((thuc va) OR (thuc dan)) thanh vai cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach y) OR (sac ky)) nang ma hoi. hieu van nam ((thuc va) OR (thuc dan)) thanh vai cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach y) or (sac ky)) nang ma hoi. hieu van nam ((thuc va) OR (thuc dan)) thanh vai cua te".
• Adding a wildcard symbol may retrieve word variants: tu ((sach y) or (sac ky)) nang ma hoi. hieu van nam ((thuc va) OR (thuc dan)) thanh vai cua te*.