Perhaps you should try some spelling variations:
than thong » than thuong, toan thong, tran thong
sach tham » sach nha
tham thuc » nham thuc, pham thuc, tam thuc
thuc cach » thuoc sach, truoc cach, tuc cac
khan tong » han tong, phan tong, khau tong
sach tren » sach tien, sach tranh
tren thuc » trien thuc, tron thuc, trinh thuc
hanh khoa » hang khoa, anh khoa, hanh hoa
khoa than » khoa luan, hoa thai, hoa tan
cach kho » bach khoa, cach thoi, cach pha
kho khan » khoa kham
tu sach » thu sach, su sach, te sach

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( tu sach tham thuc cach kho khan tong ) or ( tu sach tren thuc hanh khoa than thong ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu sach tham thuc cach kho khan tong ) OR ( tu sach tren thuc hanh khoa than thong )).
• Adding a wildcard symbol may retrieve word variants: (( tu sach tham thuc cach kho khan tong ) or ( tu sach tren thuc hanh khoa than thong ))*.