Perhaps you should try some spelling variations:
su triet » su viet, su tien, ve triet
va thanh » gia thanh, ban thanh, va tinh
va hanh » van hanh, va danh, ban hanh
hieu va » lieu va, hieu qua
su sach » so sach, vu sach
cac tuc » cac toc, cac tu, cac tac
ma hoi » mai hoi, xa hoi, ma hoa
y tang » ky tang, 6 tang, 5 tang
7 tang » 6 tang
vai su » va su, van su, lai su

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach ((y tang) OR (7 tang)) ma hoi. hieu va cac tuc ((va hanh) or (va thanh)) vai su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ((y tang) OR (7 tang)) ma hoi. hieu va cac tuc ((va hanh) OR (va thanh)) vai su triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ((y tang) OR (7 tang)) ma hoi. hieu va cac tuc ((va hanh) or (va thanh)) vai su triet".
• Adding a wildcard symbol may retrieve word variants: su sach ((y tang) OR (7 tang)) ma hoi. hieu va cac tuc ((va hanh) or (va thanh)) vai su triet*.