Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
hanh tai » thanh tai, hang tai, han tai
cac khoi » cac thoi, cac khoan, cach thoi
cam duc » cam xuc, cao duc, pham duc
cuu tre » cua tre, cau treo
va hanh » van hanh, va thanh, va danh
tu sach » thu sach, su sach, te sach
hieu ve » hieu va, hieu van
ky tang » ky nang, ky dang, kho tang
ky lang » ky nang, ky dang, tay lang
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 tang)) cac khoi. hieu ve cam duc va hanh tai ((cuu tre) or (cau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((ky lang) OR (ky tang)) cac khoi. hieu ve cam duc va hanh tai ((cuu tre) OR (cau tren)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((ky lang) OR (ky tang)) cac khoi. hieu ve cam duc va hanh tai ((cuu tre) or (cau tren))".
• Adding a wildcard symbol may retrieve word variants: tu sach ((ky lang) OR (ky tang)) cac khoi. hieu ve cam duc va hanh tai ((cuu tre) or (cau tren))*.