Perhaps you should try some spelling variations:
tham thuc » nham thuc, pham thuc, tam thuc
tay tang » tay lang, tay trung, tay quang
sach tay » xach tay, sach hay, sach nay
va danh » va dinh, va dan, dia danh
va hanh » van hanh, va thanh, ban hanh
te sach » toc sach
va tham » van tham, va cham, va thanh
hieu va » lieu va, hieu qua
tang ma » mang may, tang van
ma hoi » mai hoi, xa hoi, ma hoa
vi cau » ve cau, di cau, viet cau
va cau » van cau, va cac, va dau

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

• Performing a fuzzy search may retrieve terms with similar spellings: te sach tay tang ma hoi. hieu va tham thuc ((va hanh) or (va danh)) ((vi cau) OR (va cau)) tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach tay tang ma hoi. hieu va tham thuc ((va hanh) OR (va danh)) ((vi cau) OR (va cau)) tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach tay tang ma hoi. hieu va tham thuc ((va hanh) or (va danh)) ((vi cau) OR (va cau)) tren".
• Adding a wildcard symbol may retrieve word variants: te sach tay tang ma hoi. hieu va tham thuc ((va hanh) or (va danh)) ((vi cau) OR (va cau)) tren*.