Cloud of strings in ##IMG## [http://ej.iop.org/images/1674-1137/42/6/063105/toc_cpc_42_6_063105_ieqn1.gif] f(R) gravity - J. P. Morais Graça, Iarley P. Lobo; Ines G. Salako (Institute of Physics (IOP), 2018)
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