Added some references

Author: divyaadil23

documentation/multi_physics/user-guide/material_models/references/readme.md

@@ -1,13 +1,13 @@
 ## References
 
-<p><a id="ref-1">
-[1] Chandran KB, Rittgers SE, Yoganathan AP. <strong>Biofluid mechanics: the human circulation.</strong> CRC press; 2006 Nov 15.  </a></p>
+<p><a id="ref-1_ustruct_formulation"> <a href="https://doi.org/10.1016/j.cma.2018.03.045">
+[1] Ju Liu, Alison L. Marsden. <strong>A unified continuum and variational multiscale formulation for fluids, solids, and fluid–structure interaction.</strong> Computer Methods in Applied Mechanics and Engineering; 1 August 2018.  </a></p>
 
-<p><a id="ref-2"> <a href="https://doi.org/10.1063/1.2772250">
-[2] Boyd, Joshua, James M. Buick, and Simon Green. <strong>Analysis of the Casson and Carreau-Yasuda Non-Newtonian Blood Models in Steady and Oscillatory Flows Using the Lattice Boltzmann Method</strong>. Physics of Fluids 19, no. 9 (September 2007): 093103.</a></a></p>
+<p><a id="ref-2_derive_stress_elasticity"> <a href="https://doi.org/10.1142/S0219876218500287">
+[2] Jie Cheng and Lucy T. Zhang. <strong>A General Approach to Derive Stress and Elasticity Tensors for Hyperelastic Isotropic and Anisotropic Biomaterials</strong>. International Journal of Computational Methods; Vol. 15, No. 04, 1850028 (2018).</a></a></p>
 
-<p><a id="ref-3"> 
-[3] Vedula V, Lee J, Xu H, Kuo CC, Hsiai TK, Marsden AL.<strong> A method to quantify mechanobiologic forces during zebrafish cardiac development using 4-D light sheet imaging and computational modeling.</strong> PLoS computational biology. 2017 Oct 30;13(10):e1005828.</a></p>
+<p><a id="ref-3_hgo">  <a href="https://doi.org/10.1098/rsif.2005.0073">
+[3] T. Christian Gasser, Ray W Ogden and Gerhard A Holzapfel.<strong> Hyperelastic modelling of arterial layers with distributed collagen fibre orientations.</strong> Royal Society. 228 September 2005.</a></p>
 
 <p><a id="ref-4"> 
 [4] Mittal R, Seo JH, Vedula V, Choi YJ, Liu H, Huang HH, Jain S, Younes L, Abraham T, George RT. <strong>Computational modeling of cardiac hemodynamics: current status and future outlook.</strong> Journal of Computational Physics. 2016 Jan 15;305:1065-82. </a></p>