TY - CHAP AU - Bustince, Humberto AU - Barrenechea, Edurne AU - Fernández, Javier AU - Pagola, Miguel AU - Montero De Juan, Francisco Javier A4 - Kacprzyk, Janusz A4 - Pedrycz, Witold PY - 2015 DO - 10.1007/978-3-662-43505-2_6 SN - 978-3-662-43504-5 UR - https://hdl.handle.net/20.500.14352/35748 AB - Many different kinds of sets have been defined within the framework of fuzzy sets . This paper focusses on those fuzzy set extensions that address the difficulties that experts find in order to build the membership values. In particular, we analyze... LA - eng M2 - 89 PB - Springer TI - The Origin of Fuzzy Extensions TY - book part ER -