The fundamentals of Salvus' implementation are published in this open access article: https://doi.org/10.1093/gji/ggy469
In case you want to cite it, please use the following reference:
@article{Salvus, author = {Afanasiev, Michael and Boehm, Christian and van Driel, Martin and Krischer, Lion and Rietmann, Max and May, Dave A and Knepley, Matthew G and Fichtner, Andreas}, title = {Modular and flexible spectral-element waveform modelling in two and three dimensions}, journal = {Geophysical Journal International}, volume = {216}, number = {3}, pages = {1675-1692}, year = {2019}, doi = {10.1093/gji/ggy469} }
There are a few more articles describing specific features of Salvus.
C. Boehm, N. Korta Martiartu, N. Vinard, I. Jovanovic Balic and A. Fichtner: Time-domain spectral-element ultrasound waveform tomography using a stochastic quasi-Newton method, Proc. SPIE 10580, Medical Imaging 2018: Ultrasonic Imaging and Tomography, 105800H, 2018, doi: 10.1117/12.2293299
D. P. van Herwaarden, C. Boehm, M. Afanasiev, S. Thrastarson, L. Krischer, J. Trampert, A. Fichtner: Accelerated full-waveform inversion using dynamic mini-batches, Geophysical Journal International, 221(2), pp. 1427–1438, 2020, doi: 10.1093/gji/ggaa079
M. van Driel, C. Boehm, L. Krischer, M. Afanasiev: Accelerating numerical wave propagation using wavefield adapted meshes. Part I: forward and adjoint modelling, Geophysical Journal International, 221(3), pp. 1580–1590, 2020, doi.org: 10.1093/gji/ggaa058
S. Thrastarson, M. van Driel, L. Krischer, C. Boehm, M. Afanasiev, D. P. van Herwaarden, A. Fichtner: Accelerating numerical wave propagation by wavefield adapted meshes. Part II: full-waveform inversion, Geophysical Journal International, 221(3), pp. 1591–1604, 2020, doi: 10.1093/gji/ggaa065