Perhaps you should try some spelling variations:
te sach » toc sach
sach ty » sach y, sach tu, sach thu
ty hang » ly hang, ty xang, thi hang
hieu va » lieu va, hieu qua
cac duc » cao duc, cac dac, cac nuoc
va tinh » may tinh
hang x » nang x, hoang xa, chang xu
di cua » doi cua, de cua, do cua
x hoi » xa hoi, o hoi, x ho

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 ty hang x hoi. hieu va ((cac duc) or (cac du)) va tinh ((di cua) OR (dai cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ty hang x hoi. hieu va ((cac duc) OR (cac du)) va tinh ((di cua) OR (dai cua)) tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ty hang x hoi. hieu va ((cac duc) or (cac du)) va tinh ((di cua) OR (dai cua)) tre".
• Adding a wildcard symbol may retrieve word variants: te sach ty hang x hoi. hieu va ((cac duc) or (cac du)) va tinh ((di cua) OR (dai cua)) tre*.