Dear Ronnie, I am one of many who will always remember your mathematics, your kindness, and your friendship, and who will greatly miss you. Among other things, you created a new mathematics between category theory and topology, with groupoids and higher groupoids playing a special role in it, which is certainly appreciated but not yet fully understood… I remember, you have kindly sent me one of your Bangor preprints, after which I called you (which was the first telephone call abroad in my life) and we agreed to meet on a Topology Conference in Baku in 1987, and that you will visit Tbilisi after that. Your visit has opened many good doors… I remember Category Theory Conference in Bangor in 1989, whose Proceedings were published in 1991 as three issues of Volume 32 of “Cahiers” together with the Proceedings of its ‘second part’ in Cambridge. In the introduction of that volume, you wrote: “The pair of meetings had a high international participation, notable for the presence of nine colleagues from Tbilisi, two from Moscow and five from Eastern Europe…”. My paper submitted there was called “What is a double central extension? – The question was given by Ronnie Brown”, which you suggested to rename as “What is a double central extension? (the question was asked by Ronald Brown)”, which I did. I remember all your kind invitations to Bangor, and I am very glad we published four joint papers, in JPAA in 1997 and 1999, in APCS in 2004, and, together with George Peschke, in TAC in 2021. I am very glad Maria Manuel Clementino, Marino Gran, Timothy Porter and I edited a special volume of JHRS dedicated to you for your 80th birthday. And let me add here, I am sure you are very proud of you son Marcus, who took such an admirable care of you in your last years in this world. George Janelidze Disclaimer - University of Cape Town This email is subject to UCT policies and email disclaimer published on our website at https://www.uct.ac.za/main/email-disclaimer or obtainable from +27 21 650 9111. If this email is not related to the business of UCT, it is sent by the sender in an individual capacity. Please report security incidents or abuse via https://csirt.uct.ac.za/report-incident You're receiving this message because you're a member of the Categories mailing list group from Macquarie University. To take part in this conversation, reply all to this message. View group files<https://outlook.office365.com/owa/categories@mq.edu.au/groupsubscription.ashx?source=EscalatedMessage&action=files&GuestId=6bf90c14-94d1-45b7-a0b5-9dd447734d27> | Leave group<https://outlook.office365.com/owa/categories@mq.edu.au/groupsubscription.ashx?source=EscalatedMessage&action=leave&GuestId=6bf90c14-94d1-45b7-a0b5-9dd447734d27> | Learn more about Microsoft 365 Groups<https://aka.ms/o365g>