Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
cu tren » tu tren, dua tren
tinh va » tich va, trinh van, trinh vat
va tinh » may tinh
nam xua » nam cua, nam mua, nam qua
lang xa » lang ha, dang xay, lang van
ky lang » ky nang, ky dang, ky tang
ca tren » cau tren, la tren, co tren
xua va » xuat va, vua va, sua va

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((te sach) OR (toc sach)) ky lang xa hoi. hieu van nam xua va tinh va ((cu tren) or (ca tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) ky lang xa hoi. hieu van nam xua va tinh va ((cu tren) OR (ca tren))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) OR (toc sach)) ky lang xa hoi. hieu van nam xua va tinh va ((cu tren) or (ca tren))*".