Perhaps you should try some spelling variations:
toc sach » hoc sach, thuoc sach, nuoc sach
doc sach » hoc sach, nuoc sach, dac sac
hieu van » hieu va, thien van, lieu va
van phat » va phat, van chat, van phan
phat day » phap day, phan day, phan dau
hanh lai » hanh lam, hanh tai, thanh lap
xang ma » tang ma, nang ma, sang ma
va hanh » van hanh, va thanh, va danh
lai cua » dai cua, hai cua, lai chau
cua tre » cua te, cuu tre, cua triet
ma hoi » mai hoi, xa hoi, ma hoa

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((toc sach) OR (doc sach)) ty xang ma hoi. hieu van phat day va hanh lai cua tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) OR (doc sach)) ty xang ma hoi. hieu van phat day va hanh lai cua tre".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) OR (doc sach)) ty xang ma hoi. hieu van phat day va hanh lai cua tre*.