Perhaps you should try some spelling variations:
dau tren » dau tien, dat tren, dau tieng
nang doc » nang luc
hieu van » hieu va, thien van, lieu va
nang co » nang cao, nang noi, nang hoc
sach ky » sac ky, sach y, sach ty
nam xua » nam cua, nam mua, nam qua
va danh » va dinh, va dan, dia danh
va hanh » van hanh, va thanh, ban hanh
te sach » toc sach
vi dau » vi dai, va dau, bi dau

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: te sach ky ((nang co) OR (nang doc)) hoi. hieu van nam xua ((va danh) or (va hanh)) vi dau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ky ((nang co) OR (nang doc)) hoi. hieu van nam xua ((va danh) OR (va hanh)) vi dau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ky ((nang co) OR (nang doc)) hoi. hieu van nam xua ((va danh) or (va hanh)) vi dau tren".
• Adding a wildcard symbol may retrieve word variants: te sach ky ((nang co) OR (nang doc)) hoi. hieu van nam xua ((va danh) or (va hanh)) vi dau tren*.