Perhaps you should try some spelling variations:
vien dai » hien dai
thu sach » thuat sach, thuoc sach, thu hoach
hanh vai » hanh vi, hanh va, hanh tai
sang dai » sang tai, lang dai, sang mai
tu sach » su sach, te sach, tu cach
vai cua » dai cua, hai cua, lai cua
va hanh » van hanh, va thanh, va danh
vien da » hien dai
dai hai » dai han, dai hoi, dai tai
ky sang » ky nang, ky dang, ky tang
cua tre » cua te, cuu tre, cua triet
tuc va » thuc va, truc va, tuc xa

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 sang dai hai. hieu ((vien da) OR (vien dai)) tuc va hanh vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (thu sach)) ky sang dai hai. hieu ((vien da) OR (vien dai)) tuc va hanh vai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (thu sach)) ky sang dai hai. hieu ((vien da) OR (vien dai)) tuc va hanh vai cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (thu sach)) ky sang dai hai. hieu ((vien da) OR (vien dai)) tuc va hanh vai cua tre*.