The first of these items is an Australian review of the 1950 year Buick. This is the only Australian print item I have found. The others are all from US magazines.
1950 Motorama Postcard. http://www.damonent.com/
The Buick Magazine was sent to owners Monthly. I am not sure if there was a subscription cost on this.
The Buick Magazine was posted to owners each month. I have bought the full year from various places. A regular feature of the magazines was the centrefold where proud owners told stories about their cars.