Perhaps you should try some spelling variations:
nang khoa » hang khoa, dang khoa, nang hoa
toc sach » hoc sach, thuoc sach, nuoc sach
doc sach » hoc sach, nuoc sach, dac sac
ban hanh » ban hang
khoa hoc » hoa hoc
hieu van » hieu va, thien van, lieu va
cac dac » cac dan, cac dai, cac bac
hanh di » hanh vi, hanh de, hang di
cac duc » cac du, cao duc, cac nuoc
ty nang » ky nang, ty xang, ty hang
cua cau » cua cac, cua chu, cua cay
di cua » dai cua, doi cua, de cua

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 nang khoa hoc. hieu van ((cac duc) or (cac dac)) ban hanh di cua cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (doc sach)) ty nang khoa hoc. hieu van ((cac duc) OR (cac dac)) ban hanh di cua cau*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) OR (doc sach)) ty nang khoa hoc. hieu van ((cac duc) or (cac dac)) ban hanh di cua cau*".