Perhaps you should try some spelling variations:
cach khoan » cac khoan, cach hoan, bach khoa
sach tham » sach nha
tham thuc » nham thuc, pham thuc, tam thuc
cachh hoa » cach hoc, bach hoa, cach hoan
sach truc » cach thuc, sach tren, sach thu
truc thuc » truc thuoc, thuc thuc, truc thuy
thuc cach » thuoc sach, truoc cach, thuc hanh
khoan pho » khoan nhoi, khoan phai, khoan hoi
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 cachh hoa he thong ) or ( tu sach truc thuc cach khoan pho thong ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu sach tham thuc cachh hoa he thong ) OR ( tu sach truc thuc cach khoan pho thong )).
• Adding a wildcard symbol may retrieve word variants: (( tu sach tham thuc cachh hoa he thong ) or ( tu sach truc thuc cach khoan pho thong ))*.