Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
ty sang » ty xang, ty hang, duy sang
sang xa » song xa, lang xa, sang ma
hieu vu » hieu ve, hieu su, dieu vu
tinh ve » trinh ve, tinh ven, dinh ve
va tinh » may tinh
hieu va » lieu va, hieu qua
ve cua » le cua, de cua, te cua
cua su » qua su
soc va » hoc va, loc va, doc 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)) ty sang xa hoi. ((hieu vu) OR (hieu va)) cham soc va tinh ve cua su~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) ty sang xa hoi. ((hieu vu) OR (hieu va)) cham soc va tinh ve cua su.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) or (toc sach)) ty sang xa hoi. ((hieu vu) OR (hieu va)) cham soc va tinh ve cua su".
• Adding a wildcard symbol may retrieve word variants: ((te sach) or (toc sach)) ty sang xa hoi. ((hieu vu) OR (hieu va)) cham soc va tinh ve cua su*.