Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, am thuc, nam thu
vat dinh » va dinh, van dinh, vat sinh
dinh tai » dinh toai, dinh tri, dinh thi
hoc anh » hoc nganh, hoc nhanh, ngoc anh
ky dang » ky nang, ky danh
tai cua » thai cua, tai cuc, tri cua
ky anh » ky danh, ly anh, ty anh
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: ((toc sach) or (hoc anh)) ((ky dang) or (ky anh)) xa hoi. hieu van nam thuc vat dinh tai cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (hoc anh)) ((ky dang) OR (ky anh)) xa hoi. hieu van nam thuc vat dinh tai cua te.
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (hoc anh)) ((ky dang) or (ky anh)) xa hoi. hieu van nam thuc vat dinh tai cua te*.