Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
nam thuc » nam thuoc, am thuc, nam thu
va triet » va thiet, va trien, ve triet
ty lang » tay lang, ty hang, tu lang
qua nam » quan nam, cua nam, quang nam
danh di » danh du, xanh di, danh dien
hanh de » hanh ve, hanh kem

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

• Performing a fuzzy search may retrieve terms with similar spellings: toc sach ((ty lang) OR (ty xang)) xa hoi. hieu qua nam thuc vat ((danh di) or (hanh de)) va triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ((ty lang) OR (ty xang)) xa hoi. hieu qua nam thuc vat ((danh di) OR (hanh de)) va triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ((ty lang) OR (ty xang)) xa hoi. hieu qua nam thuc vat ((danh di) or (hanh de)) va triet".
• Adding a wildcard symbol may retrieve word variants: toc sach ((ty lang) OR (ty xang)) xa hoi. hieu qua nam thuc vat ((danh di) or (hanh de)) va triet*.