Perhaps you should try some spelling variations:
thuat sach » thuat lanh, thuat san
cau tren » cu tren, dau tren, ca tren
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
hieu van » hieu va, thien van, lieu va
cac toc » cac toi, cac thoi
danh di » danh du, xanh di, danh dien
ta danh » tac danh, tao danh, tap danh
te sach » toc sach
nang ma » tang ma, sang ma, nang cao
ma hoi » mai hoi, xa hoi, ma hoa
di cau » da cau, diem cau

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) or (thuat sach)) ky nang ma hoi. hieu van ((cac toc) OR (cac nuoc)) ta danh di cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (thuat sach)) ky nang ma hoi. hieu van ((cac toc) OR (cac nuoc)) ta danh di cau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) or (thuat sach)) ky nang ma hoi. hieu van ((cac toc) OR (cac nuoc)) ta danh di cau tren".
• Adding a wildcard symbol may retrieve word variants: ((te sach) or (thuat sach)) ky nang ma hoi. hieu van ((cac toc) OR (cac nuoc)) ta danh di cau tren*.