Perhaps you should try some spelling variations:
thuc dan » thuc hanh, hoc dan
dinh dat » dinh ket, dinh van, dinh lam
so sach » so sanh, bo sach, co sach
hieu ve » hieu va, hieu van
dat cua » dai cua, day cua, mat cua
y tang » ky tang, 7 tang, 5 tang
ve cam » ve cham, ve cac, va cam
cua te » cua tu

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 ((y tang) OR (6 tang)) xa hoi. hieu ve cam ((thuc dan) or (thuc vat)) dinh dat cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ((y tang) OR (6 tang)) xa hoi. hieu ve cam ((thuc dan) OR (thuc vat)) dinh dat cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ((y tang) OR (6 tang)) xa hoi. hieu ve cam ((thuc dan) or (thuc vat)) dinh dat cua te".
• Adding a wildcard symbol may retrieve word variants: so sach ((y tang) OR (6 tang)) xa hoi. hieu ve cam ((thuc dan) or (thuc vat)) dinh dat cua te*.