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

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