BibTeX does not have the right entry for preprints. This is a hack for producing the correct reference:
@Booklet{EasyChair:289,
author = {Reda Boumchedda and Jean-Philippe Noel and Bastien Giraud and Adam Makosiej and Marco Antonio Rios and Eduardo Esmanhotto and Emilien Bourde-Cicé and Mathis Bellet and David Turgis and Edith Beigne},
title = {Energy-Efficient 4T-based SRAM Bitcell for Ultra-Low-Voltage Operations in 28nm 3D CoolCubeTM Technology},
howpublished = {EasyChair Preprint no. 289},
doi = {10.29007/nc31},
year = {EasyChair, 2018}}
