Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hanh vai » hanh vi, hanh va, hanh tai
van hanh » van thanh, ban hanh, van anh
tu thuoc » truc thuoc, tu thuong, cua thuoc
cua tre » cua te, cua triet, dua tren
cuu tre » cau tren, cau treo
sach ty » sach y, sach tu, sach thu
nang ma » tang ma, sang ma, nang cao
ty nang » ky nang, ty xang, ty hang
ma hoi » mai hoi, xa hoi, ma hoa

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 ty nang ma hoi. hieu qua ((tu thuoc) or (cau truc)) van hanh vai ((cua tre) or (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ty nang ma hoi. hieu qua ((tu thuoc) OR (cau truc)) van hanh vai ((cua tre) OR (cuu tre)).
• Adding a wildcard symbol may retrieve word variants: toc sach ty nang ma hoi. hieu qua ((tu thuoc) or (cau truc)) van hanh vai ((cua tre) or (cuu tre))*.