Perhaps you should try some spelling variations:
hoc sach » hoc sinh, hoc cac, hoc anh
dang xay » dang van
chu tren » cu tren, chu trang, chu trong
cau tren » cu tren, dau tren, ca tren
sach ky » sac ky, sach y, sach ty
qua nam » quan nam, cua nam, quang nam
nam duc » nam duoc, pham duc, nam thuc
va danh » va dinh, va dan, va hanh
danh ve » dinh ve, hanh ve, anh ve

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

• Performing a fuzzy search may retrieve terms with similar spellings: hoc sach ky ((dang xay) or (van xay)) hoi. hieu qua nam duc va danh ve ((chu tren) OR (cau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc sach ky ((dang xay) OR (van xay)) hoi. hieu qua nam duc va danh ve ((chu tren) OR (cau tren)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc sach ky ((dang xay) or (van xay)) hoi. hieu qua nam duc va danh ve ((chu tren) OR (cau tren))".
• Adding a wildcard symbol may retrieve word variants: hoc sach ky ((dang xay) or (van xay)) hoi. hieu qua nam duc va danh ve ((chu tren) OR (cau tren))*.