Perhaps you should try some spelling variations:
hoang van » hang va
su triet » su viet, su tien, ve triet
cac thuc » cach thuc, cac thu, can thuc
lang van » dang van, tang van, giang van
xanh di » vanh dai, xanh tai
danh di » danh du, danh dien, danh gia
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
hieu ve » hieu va, hieu van
ve cac » va cac, vien cac

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 ((lang van) OR (hoang van)) hoc. hieu ve cac thuc vat ((danh di) or (xanh di)) su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky ((lang van) OR (hoang van)) hoc. hieu ve cac thuc vat ((danh di) OR (xanh di)) su triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky ((lang van) OR (hoang van)) hoc. hieu ve cac thuc vat ((danh di) or (xanh di)) su triet".
• Adding a wildcard symbol may retrieve word variants: tu sach ky ((lang van) OR (hoang van)) hoc. hieu ve cac thuc vat ((danh di) or (xanh di)) su triet*.