Perhaps you should try some spelling variations:
toc sach » doc sach, thuoc sach, nuoc sach
hanh tai » thanh tai, hang tai, han tai
hieu van » hieu va, thien van, lieu va
hoc sach » hoc sinh, hoc cac, hoc anh
ky dang » ky nang, ky danh
dang xa » dang xay, lang xa, dang ha
tai cua » thai cua, tai cuc, tri cua
tuc va » thuc va, truc va, duc va
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 sach)) ky dang xa hoi. hieu van nam ((tuc va) OR (tuc xa)) hanh tai cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (hoc sach)) ky dang xa hoi. hieu van nam ((tuc va) OR (tuc xa)) hanh tai cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) or (hoc sach)) ky dang xa hoi. hieu van nam ((tuc va) OR (tuc xa)) hanh tai cua te".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (hoc sach)) ky dang xa hoi. hieu van nam ((tuc va) OR (tuc xa)) hanh tai cua te*.