Perhaps you should try some spelling variations:
toan hanh » toan thanh, toan anh, tran hanh
thu sach » thuat sach, thuoc sach, thu hoach
duc toan » duc tan, duc ton, duc hoan
tu sach » su sach, te sach, tu cach
ve cham » va cham, ve chat, vu cham
cua tre » cua te, cuu tre, cua triet
nang ma » tang ma, sang ma, nang cao
ma hoi » mai hoi, xa hoi, ma hoa
vi cua » vai cua, di cua
ve cam » ve cac, va cam, ve cai

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) or (thu sach)) ky nang ma hoi. hieu ((ve cam) OR (ve cham)) duc toan hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (thu sach)) ky nang ma hoi. hieu ((ve cam) OR (ve cham)) duc toan hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (thu sach)) ky nang ma hoi. hieu ((ve cam) OR (ve cham)) duc toan hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (thu sach)) ky nang ma hoi. hieu ((ve cam) OR (ve cham)) duc toan hanh vi cua tre*.