Perhaps you should try some spelling variations:
manh xanh » mang xanh, anh anh, manh binh
hieu van » hieu va, thien van, lieu va
van pham » san pham, van phan, van phat
duc manh » suc manh, duc anh, duc minh
cua viet » ca viet, hoa viet, cua vat
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
xanh di » danh di, vanh dai, xanh tai
di cua » dai cua, doi cua, de cua
x hoi » xa hoi, x ho, 5 hoi
o hoi » co hoi, o hoc, o hai

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 ((x hoi) or (o hoi)). hieu van pham duc manh xanh di cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ((x hoi) OR (o hoi)). hieu van pham duc manh xanh di cua viet*.