Perhaps you should try some spelling variations:
thanh mai » thanh hai, thanh tai, thanh moi
sach ky » sach y, sach ty, sach kem
may hoi » may thoi, tay hoi, mai hoi
hieu ve » hieu va, hieu van
luc van » luoc van, luu van, luc va
duc van » duc va, duc tan, duc manh
sac ky » cac ky, sai ky
ve cam » ve cham, ve cac, va cam
thiet » thieu

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

• Performing a fuzzy search may retrieve terms with similar spellings: thuoc ((sach ky) OR (sac ky)) mang may hoi. hieu ve cam ((luc van) or (duc van)) thanh mai va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thuoc ((sach ky) OR (sac ky)) mang may hoi. hieu ve cam ((luc van) OR (duc van)) thanh mai va thiet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thuoc ((sach ky) OR (sac ky)) mang may hoi. hieu ve cam ((luc van) or (duc van)) thanh mai va thiet".
• Adding a wildcard symbol may retrieve word variants: thuoc ((sach ky) OR (sac ky)) mang may hoi. hieu ve cam ((luc van) or (duc van)) thanh mai va thiet*.