Perhaps you should try some spelling variations:
thien van » thi van
nam thuc » nam thuoc, am thuc, nam thu
thuc dan » thuc hanh, hoc dan, thuc vat
dan dinh » dang dinh, doan dinh, van dinh
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
dinh ve » dinh ket, dinh van
cua tre » cua te, cuu tre, cua triet
ve cua » le cua, de cua, te 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 ky nang ((x hoi) or (x ho)). ((lieu va) or (thien van)) nam thuc dan dinh ve cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky nang ((x hoi) OR (x ho)). ((lieu va) OR (thien van)) nam thuc dan dinh ve cua tre.
• Adding a wildcard symbol may retrieve word variants: su sach ky nang ((x hoi) or (x ho)). ((lieu va) or (thien van)) nam thuc dan dinh ve cua tre*.