Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
thuc day » thuc dan, thuc vat
va triet » va thiet, va trien, ve triet
danh hai » dang hai, lanh hai, manh hai
cua viet » ca viet, hoa viet, cua vat
hieu va » lieu va, hieu qua
thuc va » thuc vat, thuc dan
sach ty » sach y, sach tu, sach thu
ty nang » ky nang, ty xang, ty hang
nang o » nang co, nang ho, nang ro
va am » va lam, va cam
o hai » co hai, so hai, o lai

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

• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ty nang o hai. hieu va am ((thuc va) OR (thuc day)) danh hai ((va triet) OR (cua viet))~.
• Adding a wildcard symbol may retrieve word variants: toc sach ty nang o hai. hieu va am ((thuc va) or (thuc day)) danh hai ((va triet) or (cua viet))*.