diff --git a/doc/compute_pe_atom.html b/doc/compute_pe_atom.html
index 9496394e89..42704cf368 100644
--- a/doc/compute_pe_atom.html
+++ b/doc/compute_pe_atom.html
@@ -51,6 +51,12 @@ E.g. 1/4 of the dihedral energy to each of the 4 atoms.
 pairwise interactions between 1-4 atoms.  The energy contribution of
 these terms is included in the pair energy, not the dihedral energy.
 </P>
+<P>The KSpace contribution is calculated using the method in
+<A HREF = "#Heyes">(Heyes)</A> for the Ewald method and a related method for PPPM,
+as specified by the <A HREF = "kspace_style.html">kspace_style pppm</A> command.
+For PPPM, the calcluation requires 1 extra FFT each timestep that
+per-atom stress is calculated.
+</P>
 <P>As an example of per-atom potential energy compared to total potential
 energy, these lines in an input script should yield the same result
 in the last 2 columns of thermo output:
@@ -81,4 +87,10 @@ stress/atom</A>
 </P>
 <P><B>Default:</B> none
 </P>
+<HR>
+
+<A NAME = "Heyes"></A>
+
+<P><B>(Heyes)</B> Heyes, Phys Rev B 49, 755 (1994),
+</P>
 </HTML>
diff --git a/doc/compute_pe_atom.txt b/doc/compute_pe_atom.txt
index 37c5ba7c6e..3d0a6f6697 100644
--- a/doc/compute_pe_atom.txt
+++ b/doc/compute_pe_atom.txt
@@ -48,6 +48,12 @@ The "dihedral_style charmm"_dihedral_charmm.html style calculates
 pairwise interactions between 1-4 atoms.  The energy contribution of
 these terms is included in the pair energy, not the dihedral energy.
 
+The KSpace contribution is calculated using the method in
+"(Heyes)"_#Heyes for the Ewald method and a related method for PPPM,
+as specified by the "kspace_style pppm"_kspace_style.html command.
+For PPPM, the calcluation requires 1 extra FFT each timestep that
+per-atom stress is calculated.
+
 As an example of per-atom potential energy compared to total potential
 energy, these lines in an input script should yield the same result
 in the last 2 columns of thermo output:
@@ -77,3 +83,8 @@ The per-atom vector values will be in energy "units"_units.html.
 stress/atom"_compute_stress_atom.html
 
 [Default:] none
+
+:line
+
+:link(Heyes)
+[(Heyes)] Heyes, Phys Rev B 49, 755 (1994),
diff --git a/doc/compute_stress_atom.html b/doc/compute_stress_atom.html
index b0bc2e4acd..71e7444d75 100644
--- a/doc/compute_stress_atom.html
+++ b/doc/compute_stress_atom.html
@@ -75,11 +75,13 @@ other atoms in the simulation, not just with other atoms in the group.
 pairwise interactions between 1-4 atoms.  The virial contribution of
 these terms is included in the pair virial, not the dihedral virial.
 </P>
-<P>The KSpace contribution to the per-atom stress requires 6 extra FFTs
-each timestep that per-atom stress is calculated, if using the PPPM
-solver via the <A HREF = "kspace_style.html">kspace_style pppm</A> command.  Thus it
-can significantly increase the cost of the PPPM calculation if it is
-needed on a large fraction of the simulation timesteps.
+<P>The KSpace contribution is calculated using the method in
+<A HREF = "#Heyes">(Heyes)</A> for the Ewald method and a related method for PPPM,
+as specified by the <A HREF = "kspace_style.html">kspace_style pppm</A> command.
+For PPPM, the calcluation requires 6 extra FFTs each timestep that
+per-atom stress is calculated.  Thus it can significantly increase the
+cost of the PPPM calculation if it is needed on a large fraction of
+the simulation timesteps.
 </P>
 <P>Note that as defined in the formula, per-atom stress is the negative
 of the per-atom pressure tensor.  It is also really a stress*volume
@@ -119,4 +121,10 @@ options.
 </P>
 <P><B>Default:</B> none
 </P>
+<HR>
+
+<A NAME = "Heyes"></A>
+
+<P><B>(Heyes)</B> Heyes, Phys Rev B 49, 755 (1994),
+</P>
 </HTML>
diff --git a/doc/compute_stress_atom.txt b/doc/compute_stress_atom.txt
index 78dae4bda3..8e1d40d0a1 100644
--- a/doc/compute_stress_atom.txt
+++ b/doc/compute_stress_atom.txt
@@ -72,11 +72,13 @@ The "dihedral_style charmm"_dihedral_charmm.html style calculates
 pairwise interactions between 1-4 atoms.  The virial contribution of
 these terms is included in the pair virial, not the dihedral virial.
 
-The KSpace contribution to the per-atom stress requires 6 extra FFTs
-each timestep that per-atom stress is calculated, if using the PPPM
-solver via the "kspace_style pppm"_kspace_style.html command.  Thus it
-can significantly increase the cost of the PPPM calculation if it is
-needed on a large fraction of the simulation timesteps.
+The KSpace contribution is calculated using the method in
+"(Heyes)"_#Heyes for the Ewald method and a related method for PPPM,
+as specified by the "kspace_style pppm"_kspace_style.html command.
+For PPPM, the calcluation requires 6 extra FFTs each timestep that
+per-atom stress is calculated.  Thus it can significantly increase the
+cost of the PPPM calculation if it is needed on a large fraction of
+the simulation timesteps.
 
 Note that as defined in the formula, per-atom stress is the negative
 of the per-atom pressure tensor.  It is also really a stress*volume
@@ -115,3 +117,8 @@ The per-atom array values will be in pressure*volume
 "compute pe"_compute_pe.html, "compute pressure"_compute_pressure.html
 
 [Default:] none
+
+:line
+
+:link(Heyes)
+[(Heyes)] Heyes, Phys Rev B 49, 755 (1994),