Perhaps you should try some spelling variations:
hoc viet » hoc hien
vat hanh » vat thanh, van hanh, va hanh
sach ty » sach y, sach tu, sach thu
va cham » va chat, va tham
ve chat » va chat, van chat
vu sach » vu bach, su sach, vu khach
ve cham » vu cham, ve chim, viet cham
may hoi » may thoi, tay hoi, mai hoi
ty mang » ty xang, ty hang, tin mang
vi hoc » li hoc, va hoc

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

• Performing a fuzzy search may retrieve terms with similar spellings: vu sach ty mang may hoi. hieu ((((ve cham) or (ve chat))) or (va cham)) thuc vat hanh vi hoc viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu sach ty mang may hoi. hieu ((((ve cham) OR (ve chat))) OR (va cham)) thuc vat hanh vi hoc viet.
• Adding a wildcard symbol may retrieve word variants: vu sach ty mang may hoi. hieu ((((ve cham) or (ve chat))) or (va cham)) thuc vat hanh vi hoc viet*.