I recall with pleasure the many interactions I have had with Mark since we were both members, during the 1980s and 90s,  of the circulating magazine, FOLD. I n addition to writing stimulating messages and contributing diagrams to the magazine, he encouraged FOLD members to attend the  annual NYC Convention (and even planned  meetings, lunches and dinners of members during the Convention).          Over the years, it seems that Mark, with his vast array of origami pins and spirited give and take around a big table of admirers, was a presence at almost every origami convention I attended.            On a more personal level, he promoted my books and frequently notified me about  interesting books and articles on origami from  around  the world.            He will be sorely missed.           Arnold Tubis           Carlsbad, CA