Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
sach bao » sach dao, sach bai, sach bac
bao nano » tao nano, bao cao, cao nang
nano cau » nang cau, bang cau, nano va
van hanh » van thanh, ban hanh, van anh
cua tre » cua te, cuu tre, cua triet
hanh va » hang va, hanh vi
vu sach » vu bach, su sach, vu khach
cam duc » cam xuc, cao duc, nam duoc

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: vu sach bao nano cau hoi. hieu qua ((cam duc) OR (pham duc)) van hanh va ((cua tre) or (cau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu sach bao nano cau hoi. hieu qua ((cam duc) OR (pham duc)) van hanh va ((cua tre) OR (cau tren)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "vu sach bao nano cau hoi. hieu qua ((cam duc) OR (pham duc)) van hanh va ((cua tre) or (cau tren))".
• Adding a wildcard symbol may retrieve word variants: vu sach bao nano cau hoi. hieu qua ((cam duc) OR (pham duc)) van hanh va ((cua tre) or (cau tren))*.