Perhaps you should try some spelling variations:
truong doi » truong dai, trong doi, truong hoi
xa truong » cac truong
cau tren » cu tren, dau tren, ca tren
sach thu » sach thue, sach thieu, sach tham
doi cau » doi dau, di cau, doi ca
cam tuc » cam xuc, cam tu, nam thuc
hieu va » lieu va, hieu qua
sach ty » sach y, sach tu, xach tay
va cam » va cham, va cac, va cao
x hoi » xa hoi, x ho, 5 hoi
o hoi » co hoi, o hoc, o hai

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

• Performing a fuzzy search may retrieve terms with similar spellings: so ((sach ty) OR (sach thu)) nang ((x hoi) or (o hoi)). hieu va cam tuc xa truong doi cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so ((sach ty) OR (sach thu)) nang ((x hoi) OR (o hoi)). hieu va cam tuc xa truong doi cau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so ((sach ty) OR (sach thu)) nang ((x hoi) or (o hoi)). hieu va cam tuc xa truong doi cau tren".
• Adding a wildcard symbol may retrieve word variants: so ((sach ty) OR (sach thu)) nang ((x hoi) or (o hoi)). hieu va cam tuc xa truong doi cau tren*.