Perhaps you should try some spelling variations:
trinh hoa » trinh do, trinh han
dang xay » dang van, van xay
va triet » va thiet, va trien, ve triet
so sach » so sanh, bo sach, co sach
sach ky » sac ky, sach y, sach ty
hieu va » lieu va, hieu qua
tuc va » thuc va, truc va, duc va
hoa va » hoa van, hoa xa, hoa vo

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach ky ((nang x) or (dang xay)) hoi. hieu va cac ((tuc va) OR (tuc xa)) trinh hoa va triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ky ((nang x) OR (dang xay)) hoi. hieu va cac ((tuc va) OR (tuc xa)) trinh hoa va triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ky ((nang x) or (dang xay)) hoi. hieu va cac ((tuc va) OR (tuc xa)) trinh hoa va triet".
• Adding a wildcard symbol may retrieve word variants: so sach ky ((nang x) or (dang xay)) hoi. hieu va cac ((tuc va) OR (tuc xa)) trinh hoa va triet*.