Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
toc sach » hoc sach, doc sach, thuoc sach
vien cac » vien bach, vien dai, vien da
thuc day » thuc dan
hang dau » hang va, hang tai
nang xa » nang x, lang xa, nang ma
dau cua » dai cua, day cua, cau cua
cua tre » cua te, cuu tre, cua triet
y nang » ky nang, ly nang, v nang

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

• Performing a fuzzy search may retrieve terms with similar spellings: toc sach y nang xa hoi. hieu vien cac ((thuc day) OR (thuc vat)) hang dau cua tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach y nang xa hoi. hieu vien cac ((thuc day) OR (thuc vat)) hang dau cua tre".
• Adding a wildcard symbol may retrieve word variants: toc sach y nang xa hoi. hieu vien cac ((thuc day) OR (thuc vat)) hang dau cua tre*.