Perhaps you should try some spelling variations:
sach tru » sach truc, sach thu, sach tu
tru nang » tra nang, tri nang, truc nano
hieu van » hieu va, thien van, lieu va
van phat » va phat, van chat, van phan
phat duc » pham duc, phan duc, phan duoc
so sach » so sanh, bo sach, co sach
han tai » hang tai, nhan tai, van tai
va han » va phan, van han, va hanh
cua tu » cua tuc, cua su, cua cu
x hoi » o hoi, x ho, 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: so sach tru nang ((x hoi) or (xa hoi)). hieu van phat duc va han tai ((cua te) or (cua tu))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach tru nang ((x hoi) OR (xa hoi)). hieu van phat duc va han tai ((cua te) OR (cua tu)).
• Adding a wildcard symbol may retrieve word variants: so sach tru nang ((x hoi) or (xa hoi)). hieu van phat duc va han tai ((cua te) or (cua tu))*.