Perhaps you should try some spelling variations:
thuoc sach » hoc sach, nuoc sach, thuat sach
sach tren » sach tien, sach tranh
thuc bach » truc bach, thuc hanh, thi bach
thuc cach » truoc cach, thuc hanh, thu canh
chua khoa » khuan khoa, cuu khoa, cu khoa
khoa hoc » hoa hoc
tuc cac » tu cac, tich cac

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

• Performing a fuzzy search may retrieve terms with similar spellings: thuoc sach tren ((thuc bach) or (((thuc cach) OR (tuc cac)))) ((khoa hoc) or (chua khoa)) thong~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thuoc sach tren ((thuc bach) OR (((thuc cach) OR (tuc cac)))) ((khoa hoc) OR (chua khoa)) thong*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thuoc sach tren ((thuc bach) or (((thuc cach) OR (tuc cac)))) ((khoa hoc) or (chua khoa)) thong*".