  We present complete near-infrared (0.85-2.45 um), low-resolution (~100)
spectra of a sample of 26 disk L-dwarfs with reliable optical spectral type
classification. The observations have been obtained with NICS at the TNG using
a prism-based optical element (the Amici device) that provides a complete
spectrum of the source on the detector. Our observations show that
low-resolution near-infrared spectroscopy can be used to determine the spectral
classification of L-dwarfs in a fast but accurate way. We present a library of
spectra that can be used as templates for spectral classification of faint
dwarfs. We also discuss a set of near-infrared spectral indices well correlated
with the optical spectral types that can be used to accurately classify
L-dwarfs earlier than L6.
