space on stamps.. as in astronomy

Hello, tonight I was looking through some of the covers I picked up in Adelaide and thought I'd like to show you this one.

For some reason Space has been on my mind mind recently, and then today I was reminded of it when I read about the achievement of Grigory Perelman who has supposedly solved the 100-year-old Poincaré Conjecture on the properties of spheres.

Ok, nothing to do with stamps but an amazing subject area, and, I am sure, one for which many stamps have been issued.. not Poincaré's Conjecture but mathematics in general.

I think if I was to start a new thematic collection I would chose mathematics on stamps.
How interesting

So to win this cover.. what stamp issues do you know of that commemorate mathematics on stamps I will give you a few days.. say until Sunday night my time to do your research if you are interested.. whoever sends me the most number of stamp issues related in some way or another to mathematics on stamps will win this brilliant cover. usual email .. cddstamps@gmail.com plus your mailing address please.

Finally, this cover was postmarked Siding Springs, Coonabarabran.. I am rather pleased to say I have been there on an astonomy tour, amazing place.. and if you are really interested I can let you see some of the pictures I took if you email me and ask.

Enjoy your stamps, best wishes.. Michael