@article{BSL4_3_Esakia_Grigolia,
author = {Leo ESAKIA and Revaz GRIGOLIA},
title = {Christmas Trees. On Free Cyclic Algebras in Some Varieties of Closure Algebras},
journal = {Bulletin of the Section of Logic},
volume = {4},
number = {3},
year = {1975},
pages = {95--102}
}