Geodesic
On Sums of Range Symmetric Matrices in Minkowski Space
Bulletin of the Malaysian Mathematical Society, Volume 25 (2002) no. 2 
AR. Meenakshi; D. Krishnaswamy. On
                        Sums of Range Symmetric Matrices in Minkowski Space. Bulletin of the Malaysian Mathematical Society, Volume 25 (2002) no. 2. http://geodesic.mathdoc.fr/item/BMMS_2002_25_2_a4/
@article{BMMS_2002_25_2_a4,
     author = {AR. Meenakshi and D. Krishnaswamy},
     title = {On
                        {Sums} of {Range} {Symmetric} {Matrices} in {Minkowski} {Space}},
     journal = {Bulletin of the Malaysian Mathematical Society},
     year = {2002},
     volume = {25},
     number = {2},
     url = {http://geodesic.mathdoc.fr/item/BMMS_2002_25_2_a4/}
}
TY  - JOUR
AU  - AR. Meenakshi
AU  - D. Krishnaswamy
TI  - On
                        Sums of Range Symmetric Matrices in Minkowski Space
JO  - Bulletin of the Malaysian Mathematical Society
PY  - 2002
VL  - 25
IS  - 2
UR  - http://geodesic.mathdoc.fr/item/BMMS_2002_25_2_a4/
ID  - BMMS_2002_25_2_a4
ER  - 
%0 Journal Article
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%A D. Krishnaswamy
%T On
                        Sums of Range Symmetric Matrices in Minkowski Space
%J Bulletin of the Malaysian Mathematical Society
%D 2002
%V 25
%N 2
%U http://geodesic.mathdoc.fr/item/BMMS_2002_25_2_a4/
%F BMMS_2002_25_2_a4

See the original article notice from the Bulletin of the Malaysian Mathematical Sciences Society website source

We give necessary and sufficient condition for the sums of range symmetric matrices to be range symmetric in Minkowski space m . As an application it is shown that the sum and parallel sum of parallel summable range symmetric matrices are range symmetric.