Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, am thuc, nam thu
thuc dan » thuc hanh, hoc dan, thuc vat
dan tinh » doan tinh, dang tinh, dan trinh
nang xa » lang xa, nang ma, mang xa
va chua » vua chua, ca chua, va chu
tu sac » tu sach, tu cac, tu san
sac ky » cac ky, sai ky
va cua » via cua, ca cua, ma cua

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 ((nang xa) or (nang x)) hoi. hieu van nam thuc dan tinh ((va cua) OR (va chua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sac ky ((nang xa) OR (nang x)) hoi. hieu van nam thuc dan tinh ((va cua) OR (va chua)) tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sac ky ((nang xa) or (nang x)) hoi. hieu van nam thuc dan tinh ((va cua) OR (va chua)) tre".
• Adding a wildcard symbol may retrieve word variants: tu sac ky ((nang xa) or (nang x)) hoi. hieu van nam thuc dan tinh ((va cua) OR (va chua)) tre*.