kenref: cite the papers the module implements

module.yml carried an empty `dois:` list, so nothing pointed at where the method
or the implementation was published.

- 10.1021/acs.jpcb.5c08554 -- Alhossary and Smith, "Restraining Interproton
  Angular and Distance Dynamics with KEnRef", J. Phys. Chem. B 130, 3076-3087
  (2026). This introduces KEnRef and corresponds to its version 1.0.0.
- 10.1007/s10858-019-00288-8 -- Smith, Mazur, Rout, Becker, Lee and de Groot,
  "Enhancing NMR derived ensembles with kinetics on multiple timescales",
  J. Biomol. NMR 74, 27-43 (2019). The kinetic ensemble refinement method that
  KEnRef implements.

Both verified against CrossRef rather than transcribed from memory. module.md
gains the same two references in prose, so they are visible in the manual and
not only in the metadata.

Author: aalhossary

src/kenref/module.md

@@ -82,3 +82,15 @@ PRINT ARG=kenref.bias,kenref.energy,kenref.rmsd FILE=kenref.out STRIDE=1
 ```
 
 Note that there is no `ARG` keyword: KENREF biases coordinates, not collective variables.
+
+## Citing KEnRef
+
+The method this module applies, and the KEnRef implementation it calls into, are described in:
+
+- A. Alhossary and C. A. Smith, *Restraining Interproton Angular and Distance Dynamics with KEnRef*,
+  J. Phys. Chem. B **130**, 3076-3087 (2026), [doi:10.1021/acs.jpcb.5c08554](https://doi.org/10.1021/acs.jpcb.5c08554).
+  This paper introduces KEnRef and corresponds to its version 1.0.0.
+- C. A. Smith, A. Mazur, A. K. Rout, S. Becker, D. Lee, B. L. de Groot,
+  *Enhancing NMR derived ensembles with kinetics on multiple timescales*,
+  J. Biomol. NMR **74**, 27-43 (2019), [doi:10.1007/s10858-019-00288-8](https://doi.org/10.1007/s10858-019-00288-8).
+  This is the kinetic ensemble refinement method that KEnRef implements.

src/kenref/module.yml

@@ -1,6 +1,8 @@
 name: kenref
 authors: Amr Alhossary and Colin Smith
 description: kinetic ensemble refinement of a replica ensemble against NMR observables
-dois: []
+dois:
+  - 10.1021/acs.jpcb.5c08554
+  - 10.1007/s10858-019-00288-8
 tags:
   KENREF: bias that restrains an ensemble of replicas against NMR relaxation observables