Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
tang mai » tang ma, tang tai, lang mai
van hanh » van thanh, ban hanh, van anh
thu sach » tu sach, thuat sach, thuoc sach
ky tang » ky nang, ky dang, kho tang
mai hoi » mai khoi, dai hoi, lai hoi
qua cac » cua cac
cac duc » cac du, cao duc, cac dac
duc van » duc va, duc tan, duc manh
cua tre » cuu tre, cua triet, dua tren
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: ((toc sach) or (thu sach)) ky tang mai hoi. hieu qua cac duc van hanh vi ((cua tre) or (cua te))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (thu sach)) ky tang mai hoi. hieu qua cac duc van hanh vi ((cua tre) OR (cua te)).
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (thu sach)) ky tang mai hoi. hieu qua cac duc van hanh vi ((cua tre) or (cua te))*.