@article{PenaStastinskaEstebanetal.1998,
  author    = {Pena, M. and Stastinska, G. and Esteban, C. and Koesterke, Lars and Medina, S. and Kingsburgh, R.},
  title     = {Galactic planetary nebulae with Wolf-Rayet nuclei : I. Objects with [WC]-early type stars},
  year      = {1998},
  language  = {en}
}
@article{HoulahanCurrieCottenieetal.2007,
  author    = {Houlahan, Jeff E. and Currie, David J. and Cottenie, Karl and Cumming, Graeme S. and Ernest, S. K. Morgan and Findlay, C. Scott and Fuhlendorf, Samuel D. and Gaedke, Ursula and Legendre, Pierre and Magnuson, John J. and McArdle, Brian H. and Muldavin, Esteban H. and Noble, David and Russell, Robert and Stevens, Richard D. and Willis, Trevor J. and Woiwod, Ian P. and Wondzell, Steve M.},
  title     = {Compensatory dynamics are rare in natural ecological communities},
  issn      = {0027-8424},
  doi       = {10.1073/pnas.0603798104},
  year      = {2007},
  abstract  = {In population ecology, there has been a fundamental controversy about the relative importance of competition- driven (density-dependent) population regulation vs. abiotic influences such as temperature and precipitation. The same issue arises at the community level; are population sizes driven primarily by changes in the abundances of cooccurring competitors (i.e., compensatory dynamics), or do most species have a common response to environmental factors? Competitive interactions have had a central place in ecological theory, dating back to Gleason, Volterra, Hutchison and MacArthur, and, more recently, Hubbell's influential unified neutral theory of biodiversity and biogeography. If competitive interactions are important in driving year-to-year fluctuations in abundance, then changes in the abundance of one species should generally be accompanied by compensatory changes in the abundances of others. Thus, one necessary consequence of strong compensatory forces is that, on average, species within communities will covary negatively. Here we use measures of community covariance to assess the prevalence of negative covariance in 41 natural communities comprising different taxa at a range of spatial scales. We found that species in natural communities tended to covary positively rather than negatively, the opposite of what would be expected if compensatory dynamics were important. These findings suggest that abiotic factors such as temperature and precipitation are more important than competitive interactions in driving year-to-year fluctuations in species abundance within communities.},
  language  = {en}
}
@article{PenaStastinskaEstebanetal.1999,
  author    = {Pena, M. and Stastinska, G. and Esteban, C. and Koesterke, Lars and Medina, S. and Kingsburgh, R.},
  title     = {Spectroscopy of planetary nebulae with [WR] nuclei},
  year      = {1999},
  language  = {en}
}
@article{MesaDelgadoEstebanGarciaRojas2015,
  author    = {Mesa-Delgado, A. and Esteban, C. and Garc{\´i}a-Rojas, J.},
  title     = {Ring Nebulae},
  series = {Wolf-Rayet Stars : Proceedings of an International Workshop held in Potsdam, Germany, 1.-5. June 2015},
  journal   = {Wolf-Rayet Stars : Proceedings of an International Workshop held in Potsdam, Germany, 1.-5. June 2015},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-88299},
  pages     = {325 -- 328},
  year      = {2015},
  abstract  = {Preliminary results are presented from spectroscopic data in the optical range of the Galactic ring nebulae NGC 6888, G2:4+1:4, RCW 58 and Sh2-308. Deep observations with long exposure times were carried out at the 6.5m Clay Telescope and at the 10.4m Gran Telescopio Canarias. In NGC 6888, recombination lines of C ii, O ii and N ii are detected with signal-to-noise ratios higher than 8. The chemical content of NGC 6888 is discussed within the chemical enrichment predicted by evolution models of massive stars. For all nebulae, a forthcoming work will content in-depth details about observations, analysis and final results (Esteban et al. 2015, in prep.).},
  language  = {en}
}