Kira V. Adaricheva Ralph McKenzie Eric Richard Zenk Miklós Maróti James B. Nation The Jónsson-Kiefer Property. 111-131 2006 83 Studia Logica 1-3 http://dx.doi.org/10.1007/s11225-006-8300-x db/journals/sLogica/sLogica83.html#AdarichevaMZMN06