My impression of these laboratories was that there was no real purpose to the research being done. Most of the work seemed repetitive, something that someone else had already done. But such is the environment when you don't really have to fight and claw for grant money to study the chemistry of your ideas.
The only new thing on the return train trip was that border officers did enter the passenger car and demanded to see our passports. Themen had warned us about the possibility that this might happen. However he claimed this was only a formality and they would surely let us through. Susan and I were carrying American passports at the time since we had become US citizens in 1968. American passports were always treated with respect in any country we traveled and we had no trouble with the guards.
Over the subsequent years I tried to stop at the Amsterdam airport whenever possible to have a coffee with Professor DeBoer. I remember once where he took me to a small restaurant, his favourite, placed so low to the ground that the water level of the canal bordering the building was higher than where we sat. I remarked to him about that. He simply laughed at my worries, that at any time we might be inundated. We just liked each other's company.
The last time I saw Themen he would not meet me at the airport terminal itself. He said I should simply walk out the main door and there I would see a hotel. This hotel had a coffee bar. He would be sitting there waiting for me. Parking was free for customers. He preferred this place because of parking. He hated the ritual of finding a parking spot at the airport, walking forever to the terminal and paying for a few minutes with outrageous money. I did as I was told and we met and shared his preferred brand of java. Now I noticed Themen's demeanor. Nervousness had become an illness.
Although Themen DeBoer was older than me we were kindred spirits. We didn't have to talk much. We understood where we had come from and where we were at the time. That was enough. Not much later I heard Themen had died. Died of heart problems. He never told me.