Before the Internet, academics used to send each other postcards to request copies of papers.
Pictured above is Dr. Ming-Tsuen Hsieh at a research talk in Beijing in October 2000. Below are some of the postcards he received from academics and their institutions, dating back to the 1980s.
Some of the following postcards feature the two following papers:
London, United Kingdom
Chicago IL, United States
Novo Mesto, Yugoslavia (!)
New York NY, United States
Edmonton AB, Canada
Montréal QC, Canada
Durham NC, United States
Philadelphia PA, United States
Prague, Czechoslovakia (!)
New Haven CT, United States
Los Angeles CA, United States
Detroit MI, United States
Dr. Ming-Tsuen Hsieh's postcards can be viewed here.