Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu cua » hieu qua, dieu cua, bieu cua
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
ban hanh » ban hang
dang hoa » dang hoai, dang khoa, dong hoa
ky dang » ky nang, ky danh
sach ky » sac ky, sach y, sach ty
va danh » va dinh, va dan, va hanh
vi cua » vai cua
di cua » dai cua, doi cua, de cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: toc sach ky dang hoa hoc. hieu cua cac nuoc ((ban hanh) or (va danh)) ((vi cua) or (di cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky dang hoa hoc. hieu cua cac nuoc ((ban hanh) OR (va danh)) ((vi cua) OR (di cua)) tre.
• Adding a wildcard symbol may retrieve word variants: toc sach ky dang hoa hoc. hieu cua cac nuoc ((ban hanh) or (va danh)) ((vi cua) or (di cua)) tre*.