Bo Lehnert wrote to M.W. Evans here:
Concerning the point on the gauge process made by Gerhard Bruhn on the work by Sisir and
myself, I had at that time a discussion with Bruhn. His point was due to a misunderstanding,
and the discussion was settled at the beginning of Section 2 in his paper of Physica Scripta
Hence Lehnert refers to Section 2 of that paper  as the basis of a settlement with Bruhn.
The essential phrases are:
The authors of  were Bo Lehnert and Sisir Roy, the leading author of  was Myron W. Evans.
(a) The ‘Lorenz-free’ case: Without Lorenz gauge (1.3) the Ampère–Maxwell equation Ñ × H = j + Dt is equivalent to equation
(1.1) 1/c² Att − ΔA + Ñ (Ñ·A + 1/c² Φt) = μo j .
(b) The case of Lorenz gauge: With Lorenz gauge (1.3) the Ampère–Maxwell equation Ñ × H = j + Dt is equivalent to equation
(1.4) 1/c² Att − ΔA = μo j .
. . .
The authors of  refer to a former paper  where two of them had described the gauge process quite correctly not differing from the textbooks. However, as we shall see, the leading author of  has made a wrong use of the equations in  by confusing the above cases (a) and (b).
He is intending to treat the vacuum case, where no charge and no current is present, of ‘classical electrodynamics without the Loren(t)z condition’, i.e. he considers case (a). So he starts with the reduced ‘Lorenz free’ equation (1.1) with j = 0, with the equation
1/c² Att − ΔA + Ñ (Ñ·A + 1/c² Φt) = 0 , (2.1)
and, having in mind the Lorenz gauged version (1.4), he defines a ‘vacuum current’ jA by his equation
− (Ñ·A + 1/c² Φt) =: μo jA. [2;(10)]
Therewith equation (2.1) takes the form
1/c² Att − ΔA = μo jA. (2.2)
Now we come to the magic trick: our author remembers equation (2.2) to belong to the Ampère–Maxwell equation and so he concludes
Ñ × H = jA + Dt , [2;(20)]
ignoring that this is true only under Lorenz gauge (case (b)) while he had decided to consider the Lorenz-free case (a).
For the way back to the Ampère–Maxwell equation the Lorenz term (1.3) is essential and must be ‘reimbursed’, i.e. correctly we have to start with the Lorenz-free version of equation (2.2), i.e. with
1/c² Att − ΔA + Ñ (Ñ·A + 1/c² Φt) = μo j := μo jA + Ñ (Ñ·A + 1/c² Φt) (2.3)
to obtain the Ampère–Maxwell equation Ñ × H = j + Dt . However, due to equation (2.3) and the definition [1; (10)] of the vacuum current jA we have
μo j = μo jA + Ñ (Ñ·A + 1/c² Φt) = 0, (2.4)
thus, the correct calculation yields the ZERO vacuum current j = 0.
 Lehnert B and Roy S 1997 Extended Electromagnetic Theory...;
APEIRON vol 4, no 2–3, online at
 Evans M W 2000 Classical electrodynamics without the Lorentz
extracting energy from the vacuum Phys. Scr. 61 513–7 online at
abstract: http://www.physica.org/ xml/article.asp?article=v061a00513.xml and
PDF full text: http://www.physica.org/asp/document.asp? article=v061p05a00513
 G.W. Bruhn, No Energy to be Extracted from the Vacuum,
Phys. Scr. Vol. 74, 535-536 , 2006,
see the detailed quote in
(09.07.2007) Bo Lehnert Correcting M.W. Evans' Distortions
(05.07.2007) Evans' Misunderstanding of Lehnert's Settlement with Bruhn
(04.07.2007) A Reply to a "Rebuttal" by MWE on Vacuum Currents