Perhaps you should try some spelling variations:
tham thuc » nham thuc, pham thuc, tam thuc
hanh kien » danh kien, anh kien, thanh vien
su triet » su viet, su tien, ve triet
dang mau » dong mau, dang van, dang su
thuc van » thuc vat, thuc dan, thuc va
hanh ki » hanh vi, hanh ky, thanh kim
tu sach » thu sach, su sach, te sach
sach vu » sach va, sach tu, sach uu
hieu va » lieu va, hieu qua
dang ma » dang mam, dang mat, tang ma
va tham » van tham, va cham, va thanh

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 vu ((dang ma) or (dang mau)) hoi. hieu va tham thuc van ((hanh ki) OR (hanh kien)) su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach vu ((dang ma) OR (dang mau)) hoi. hieu va tham thuc van ((hanh ki) OR (hanh kien)) su triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach vu ((dang ma) or (dang mau)) hoi. hieu va tham thuc van ((hanh ki) OR (hanh kien)) su triet".
• Adding a wildcard symbol may retrieve word variants: tu sach vu ((dang ma) or (dang mau)) hoi. hieu va tham thuc van ((hanh ki) OR (hanh kien)) su triet*.