Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
cay phoi » cap phoi, tay hoi, cay cho
lang phi » lang phu, lang chai, lang ha
phi cua » phai cua, chi cua, khi cua
duc ban » duc van, dua ban, duc man
so sach » so sanh, bo sach, co sach
van bao » van ban, van dao
sach ky » sac ky, sach y, sach ty
ky dang » ky nang, ky danh
cua tre » cua te, cuu tre, cua triet

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 ky dang ((cay phoi) or (cap cho)). hieu van bao ((duc ban) OR (duc tan)) lang phi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ky dang ((cay phoi) OR (cap cho)). hieu van bao ((duc ban) OR (duc tan)) lang phi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ky dang ((cay phoi) or (cap cho)). hieu van bao ((duc ban) OR (duc tan)) lang phi cua tre".
• Adding a wildcard symbol may retrieve word variants: so sach ky dang ((cay phoi) or (cap cho)). hieu van bao ((duc ban) OR (duc tan)) lang phi cua tre*.