Perhaps you should try some spelling variations:
nang hanh » nang thanh, dang hanh, nang hang
tang hanh » tang thanh, dang hanh, thang thanh
hieu van » hieu va, thien van, lieu va
cam duc » cam xuc, cao duc, pham duc
van cam » van nam, van lam, van cau
sach ty » sach y, sach tu, sach thu
nang ma » tang ma, sang ma, nang cao
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: tu ((sach ty) or (cac ky)) nang ma hoi. hieu van cam duc ((tang hanh) OR (nang hanh)) dai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach ty) OR (cac ky)) nang ma hoi. hieu van cam duc ((tang hanh) OR (nang hanh)) dai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach ty) or (cac ky)) nang ma hoi. hieu van cam duc ((tang hanh) OR (nang hanh)) dai cua tre".
• Adding a wildcard symbol may retrieve word variants: tu ((sach ty) or (cac ky)) nang ma hoi. hieu van cam duc ((tang hanh) OR (nang hanh)) dai cua tre*.