Perhaps you should try some spelling variations:
toc sach » doc sach, thuoc sach, nuoc sach
hoc sach » hoc sinh, hoc cac, hoc anh
hieu van » hieu va, thien van, lieu va
cam thuc » am thuc, nam thuc, cam thu
tinh tai » trinh tai, tinh thai, tinh hai
cau tren » cu tren, dau tren, ca tren
van cam » van nam, van lam, van cau
thuc va » thuc vat, thuc dan, thuc day
va tinh » may tinh
tai cau » tai cac, tai cao
x hoi » xa hoi, o hoi, x ho

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) OR (hoc sach)) ky nang x hoi. hieu van cam thuc va tinh tai cau tren~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) OR (hoc sach)) ky nang x hoi. hieu van cam thuc va tinh tai cau tren".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) OR (hoc sach)) ky nang x hoi. hieu van cam thuc va tinh tai cau tren*.