Perhaps you should try some spelling variations:
sach thu » sach thue, sach thieu, sach tham
thu nang » thi nang, thu hang, thu bang
hieu cua » hieu qua, bieu cua, hieu ca
dieu cua » dieu tra
nhan tuc » nhan thuc, nhan luc, nhanh thuc
te sach » toc sach
han tai » hang tai, nhan tai, van tai
tai cua » thai cua, tai cuc, tri cua
tuc va » thuc va, truc va, tuc xa
va han » va phan, van han, va hanh
cua tu » cua tuc, cua su, cua cu
x hoi » xa hoi, o hoi, 5 hoi

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 thu nang ((x hoi) or (x ho)). ((hieu cua) OR (dieu cua)) nhan tuc va han tai cua tu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach thu nang ((x hoi) OR (x ho)). ((hieu cua) OR (dieu cua)) nhan tuc va han tai cua tu.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach thu nang ((x hoi) or (x ho)). ((hieu cua) OR (dieu cua)) nhan tuc va han tai cua tu".
• Adding a wildcard symbol may retrieve word variants: te sach thu nang ((x hoi) or (x ho)). ((hieu cua) OR (dieu cua)) nhan tuc va han tai cua tu*.