Perhaps you should try some spelling variations:
xanh dien » danh dien, nganh dien, nhanh dien
thu sach » tu sach, thuat sach, thuoc sach
hieu van » hieu va, thien van, lieu va
cau tren » cu tren, dau tren, ca tren
cau hoc » cau hoi, cao hoc, cuu hoc
sach ky » sac ky, sach y, sach ty
cau hoa » cau hoi
xanh di » danh di, vanh dai, xanh tai
lang xa » lang ha, dang xay, lang van
ky lang » ky nang, ky dang, ky tang

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: thu sach ky lang xa hoi. hieu van ((cau hoc) OR (cau hoa)) va ((xanh di) or (xanh dien)) cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ky lang xa hoi. hieu van ((cau hoc) OR (cau hoa)) va ((xanh di) OR (xanh dien)) cau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach ky lang xa hoi. hieu van ((cau hoc) OR (cau hoa)) va ((xanh di) or (xanh dien)) cau tren".
• Adding a wildcard symbol may retrieve word variants: thu sach ky lang xa hoi. hieu van ((cau hoc) OR (cau hoa)) va ((xanh di) or (xanh dien)) cau tren*.