I lifted the train’s window and reached out to see my students. Six were standing there, five Polish girls and a Polish boy in their 20’s, each held a Vietnam postcard. They waved their hands at me. Their eyes were full of tears, even the boy – who I gave a red lipstick print from a kiss on the postcard. Tears filled my eyes.

Just an hour before that we were all sitting on the green grass grown in the yard of Krakow’s University of Economics, under the warm sunlight of early May, in the last class of the course. There I asked them to look carefully around for a minute, and then close their eyes. “How many lines of trees are there on your right?” I began to ask.