The family has asked that I speak about Ivan's years in Calgary and I am honoured to do so.

Ivan and Hetje arrived in Calgary in the fall of 1975 fresh from postdoctoral appointments at Cal Tech and Darmstadt. He had received his PhD from the University of Manitoba where he had been part of George Gratzer's research group, studying lattice theory and universal algebra. Ivan's dissertation, really a compendium of many research papers completed as a graduate student, opened a new stream in lattice theory, one that emphasized the order and graph-theoretic aspects of the subject.

I came to Calgary at the same time, with vague plans to study with Eric Milner. But Richard Guy alerted me to the arrival of a dynamic young researcher -- responsible, Richard said, for a new blend of combinatorics and lattice theory. Ivan offered a graduate course and we began, immediately, to work together. Many hours every week, often many hours each day, often followed by dinner and conversation with Hetje and their new son Rob. Rob didn't contribute much at first, but that would change.

It was a very exciting time for those involved in the new subject -- Order Theory -- and Ivan was very much in the lead. He was responsible for forging a new research community. We met the Lyonnaise mathematicians -- Maurice Pouzet, Robert Bonnet and others trained by Professors Corominas and Fraisse. Ivan had made friendships and founded collaborations with Rudolf Wille's group in Darmstadt and with Robert Dilworth and others at Cal Tech. There were other exotic visitors to Calgary -- the Hungarians, the Manitobans ... Bill Sands eventually came to Calgary and stayed.

Ivan's influence and energy are epitomized by the first Banff conference on order and lattice theory, held in the fall of 1981. As always, Ivan saw this effort in a clear historical context, as a continuation of the pioneering lattice theory meetings in Charlottesville in 1938 and in Monterey in 1959. For just about two weeks, a diverse group of more than 100 met at the Banff Conference Center. With day long formal programs, evening problem sessions and nonstop mathematics. It was a wonderful opportunity to see the leaders of our mathematical world: Paul Erdos, Garrett Birkhoff, Robert Dilworth, Bjarni Jonsson, Richard Stanley, Rudolf Wille, to name just some. The meeting remains a mathematical and personal high point for many of us. And it was a critical point, engineered by Ivan, in the genesis of order theory. But one of my favourite memories is of Rob explaining to Ivan that Professor Birkhoff didn't mind one bit that Rob called him "Garrett" while they played frisbee. Hetje was amused; I'm not sure Ivan was.

Life at the University of Calgary in the late 1970's and early 1980's was magical for a young mathematician. Like most of the young, I was too self-absorbed and too busy to realize how wonderful it was. So much of this was due to Ivan, to his energy and focus, and to his and Hetje's generosity.

We are formed by our families, our friends and our teachers. Ivan was my teacher, Ivan and Hetje, my friends.