Perhaps you should try some spelling variations:
cham thuc » nham thuc, pham thuc, tham thuc
hieu van » hieu va, thien van, lieu va
van cham » van chat, van tham, va cham
thuc day » thuc dan, thuc vat
day hanh » day nhanh, day thanh, dao hanh
su sach » so sach, vu sach
sach ty » sach y, sach tu, sach thu
ty nang » ky nang, ty xang, ty hang
cua tre » cua te, cuu tre, cua triet
vi cua » vai cua, di cua
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: su sach ty nang ((x hoi) OR (x ho)). hieu van cham thuc day hanh vi cua tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ty nang ((x hoi) OR (x ho)). hieu van cham thuc day hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach ty nang ((x hoi) OR (x ho)). hieu van cham thuc day hanh vi cua tre*.