===Letters=== If you want to send a standard letter by regular mail, you can put it at the Reception on the ground floor. Make sure that you affix the Observatory barcode and return address on the backside and write receiver's address in the middle on the front of your letter. Stickers can be collected at the Secretariat. Would you like to send out registered letters? Please write down a SAP number as well for internal use. ===Packages==== If you need to send a package by courier, contact the Secretariat. Make sure you have a SAP number for the costs involved. You can contact Nancy Zhou for sending out posts .