Perhaps you should try some spelling variations:
cac khoi » cac thoi, cac khoan, cach thoi
hanh tai » thanh tai, hang tai, han tai
dau tren » dau tien, dat tren, dau tieng
tu sach » thu sach, su sach, te sach
ky lang » ky dang, ky tang, tay lang
hieu ve » hieu va, hieu van
cam duc » cam xuc, cao duc, pham duc
va hanh » van hanh, va thanh, va danh
cuu tre » cua tre, cau tren, cau treo
ve cam » ve cham, ve cac, va cam

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 ((ky lang) OR (ky nang)) cac khoi. hieu ve cam duc va hanh tai ((cuu tre) or (dau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((ky lang) OR (ky nang)) cac khoi. hieu ve cam duc va hanh tai ((cuu tre) OR (dau tren)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((ky lang) OR (ky nang)) cac khoi. hieu ve cam duc va hanh tai ((cuu tre) or (dau tren))".
• Adding a wildcard symbol may retrieve word variants: tu sach ((ky lang) OR (ky nang)) cac khoi. hieu ve cam duc va hanh tai ((cuu tre) or (dau tren))*.