@article{Cintula200740,
title = "Formal systems of fuzzy logic and their fragments",
journal = "Annals of Pure and Applied Logic",
volume = "150",
number = "1--3",
pages = "40--65",
year = "2007",
note = "",
issn = "0168-0072",
doi = "10.1016/j.apal.2007.09.002",
url = "http://www.sciencedirect.com/science/article/pii/S0168007207000772",
author = "Petr Cintula and Petr H{\'{a}}jek and Rostislav Hor{\v{c}}{\'{\i}}k",
keywords = "Mathematical fuzzy logic",
keywords = "BCK-algebras",
keywords = "BCK",
keywords = "FBCK",
keywords = "Monoidal   t  -norm based logic"
}