  Twenty years ago, GRB 980425/SN 1998bw revealed that long Gamma-Ray Bursts
(GRBs) are physically associated with broad-lined type Ic supernovae. Since
then more than 1000 long GRBs have been localized to high angular precision,
but only in about 50 cases the underlying supernova (SN) component was
identified. Using the multi-channel imager GROND (Gamma-Ray Burst Optical
Near-Infrared Detector) at ESO/La Silla, during the last ten years we have
devoted a substantial amount of observing time to reveal and to study SN
components in long-GRB afterglows. Here we report on four more GRB-SNe
(associated with GRBs 071112C, 111228A, 120714B, and 130831A) which were
discovered and/or followed-up with GROND and whose redshifts lie between z=0.4
and 0.8. We study their afterglow light curves, follow the associated SN bumps
over several weeks, and characterize their host galaxies. Using SN 1998bw as a
template, the derived SN explosion parameters are fully consistent with the
corresponding properties of the so-far known GRB-SN ensemble, with no evidence
for an evolution of their properties as a function of redshift. In two cases
(GRB 120714B/SN 2012eb at z=0.398 and GRB 130831A/SN 2013fu at z=0.479)
additional Very Large Telescope (VLT) spectroscopy of the associated SNe
revealed a photospheric expansion velocity at maximum light of about 40 000 and
20 000 km/s, respectively. For GRB 120714B, which was an
intermediate-luminosity burst, we find additional evidence for a blackbody
component in the light of the optical transient at early times, similar to what
has been detected in some GRB-SNe at lower redshifts.
