Perhaps you should try some spelling variations:
nam thuc » nam thuoc, am thuc, nam thu
thuc dan » thuc hanh, hoc dan, thuc vat
hieu ve » hieu va, hieu van
dan dan » dang dan, ban dan, dao dan
vu sac » vu sach, vu san, va sac
sac ky » cac ky, sai ky
ve nam » he nam, va nam, le nam
di cuu » di cau, dinh cuu
di cua » dai cua, doi cua, de cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: vu sac ky nang ((x ho) or (xa hoi)). hieu ve nam thuc dan dan ((di cuu) OR (di cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu sac ky nang ((x ho) OR (xa hoi)). hieu ve nam thuc dan dan ((di cuu) OR (di cua)) tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "vu sac ky nang ((x ho) or (xa hoi)). hieu ve nam thuc dan dan ((di cuu) OR (di cua)) tre".
• Adding a wildcard symbol may retrieve word variants: vu sac ky nang ((x ho) or (xa hoi)). hieu ve nam thuc dan dan ((di cuu) OR (di cua)) tre*.