Perhaps you should try some spelling variations:
toc sach » doc sach, thuoc sach, nuoc sach
thu nang » thi nang, thu hang, thu bang
cac truc » cau truc, cac tru, cac trung
hoc sach » hoc sinh, hoc cac, hoc anh
nang xa » nang x, lang xa, nang ma
qua cac » cua cac
truc va » thuc va, thuc vat, trung va
hang vi » hang va, hanh vi, khang voi
hang di » hang doi, hang dien, hang dich
cua tre » cua te, cuu tre, cua triet

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)) thu nang xa hoi. hieu qua cac truc va ((hang vi) or (hang di)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (hoc sach)) thu nang xa hoi. hieu qua cac truc va ((hang vi) OR (hang di)) cua tre.
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (hoc sach)) thu nang xa hoi. hieu qua cac truc va ((hang vi) or (hang di)) cua tre*.