Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
hanh doi » thanh doi, hanh noi, hang doi
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
nang ra » nang ma, lang ra, nang ro
cam tuc » cam tu, nam thuc, dam thuc
doi cua » dai cua, hoi cua
cua te » cua tu

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 ((nang cao) or (nang ra)) hoi. hieu qua ((cam tuc) OR (cam xuc)) van hanh doi cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky ((nang cao) OR (nang ra)) hoi. hieu qua ((cam tuc) OR (cam xuc)) van hanh doi cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky ((nang cao) or (nang ra)) hoi. hieu qua ((cam tuc) OR (cam xuc)) van hanh doi cua te".
• Adding a wildcard symbol may retrieve word variants: tu sach ky ((nang cao) or (nang ra)) hoi. hieu qua ((cam tuc) OR (cam xuc)) van hanh doi cua te*.