deletions | additions       diff --git a/bibliography/biblio.bib b/bibliography/biblio.bib  index a8d8278..ab224ca 100644  --- a/bibliography/biblio.bib  +++ b/bibliography/biblio.bib 
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title = {{Zero-variance zero-bias principle for observables in quantum Monte Carlo: Application to forces}},  journal = {The Journal of Chemical Physics},  }  @article{Li_2007,  doi = {10.1016/j.cplett.2007.07.100},  url = {http://dx.doi.org/10.1016/j.cplett.2007.07.100},  year = {2007},  month = {sep},  publisher = {Elsevier {BV}},  volume = {445},  number = {4-6},  pages = {345--349},  author = {Yu Li and Jan Vrbik and Stuart M. Rothstein},  title = {{Towards a field-free quantum Monte Carlo approach to polarizabilities of excited states: Application to the n=2 hydrogen atom}},  journal = {Chemical Physics Letters},  }