Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
dua tren » dung tren
su sach » so sach, vu sach
ky dang » ky nang, ky danh
dang xa » dang xay, lang xa, dang ha
hieu ke » hieu kem, chieu ke, hieu ky
truc va » thuc va, thuc vat, trung va
va lanh » va lang, va danh, va hanh
ke cau » ket cau
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: ((su sach) or (toc sach)) ky dang xa hoi. hieu ke cau truc va lanh dao ((dua tren) or (cua te))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sach) OR (toc sach)) ky dang xa hoi. hieu ke cau truc va lanh dao ((dua tren) OR (cua te)).
• Adding a wildcard symbol may retrieve word variants: ((su sach) or (toc sach)) ky dang xa hoi. hieu ke cau truc va lanh dao ((dua tren) or (cua te))*.