```--- a
+++ b/src/SB03OV.f
@@ -0,0 +1,105 @@
+      SUBROUTINE SB03OV( A, B, C, S )
+C
+C     SLICOT RELEASE 5.0.
+C
+C     Copyright (c) 2002-2009 NICONET e.V.
+C
+C     This program is free software: you can redistribute it and/or
+C     modify it under the terms of the GNU General Public License as
+C
+C     This program is distributed in the hope that it will be useful,
+C     but WITHOUT ANY WARRANTY; without even the implied warranty of
+C     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+C     GNU General Public License for more details.
+C
+C     You should have received a copy of the GNU General Public License
+C     along with this program.  If not, see
+C
+C     PURPOSE
+C
+C     To construct a complex plane rotation such that, for a complex
+C     number  a  and a real number  b,
+C
+C        ( conjg( c )  s )*( a ) = ( d ),
+C        (       -s    c ) ( b )   ( 0 )
+C
+C     where  d  is always real and is overwritten on  a,  so that on
+C     return the imaginary part of  a  is zero.  b  is unaltered.
+C
+C     This routine has A and C declared as REAL, because it is intended
+C     for use within a real Lyapunov solver and the REAL declarations
+C     mean that a standard Fortran DOUBLE PRECISION version may be
+C     readily constructed.  However A and C could safely be declared
+C     COMPLEX in the calling program, although some systems may give a
+C     type mismatch warning.
+C
+C     ARGUMENTS
+C
+C     Input/Output Parameters
+C
+C     A       (input/output) DOUBLE PRECISION array, dimension (2)
+C             On entry, A(1) and A(2) must contain the real and
+C             imaginary part, respectively, of the complex number a.
+C             On exit, A(1) contains the real part of d, and A(2) is
+C             set to zero.
+C
+C     B       (input) DOUBLE PRECISION
+C             The real number b.
+C
+C     C       (output) DOUBLE PRECISION array, dimension (2)
+C             C(1) and C(2) contain the real and imaginary part,
+C             respectively, of the complex number c, the cosines of
+C             the plane rotation.
+C
+C     S       (output) DOUBLE PRECISION
+C             The real number s, the sines of the plane rotation.
+C
+C     CONTRIBUTOR
+C
+C     Release 3.0: V. Sima, Katholieke Univ. Leuven, Belgium, Aug. 1997.
+C     Supersedes Release 2.0 routine SB03CV by Sven Hammarling,
+C     NAG Ltd., United Kingdom, May 1985.
+C
+C     REVISIONS
+C
+C     Dec. 1997.
+C
+C     KEYWORDS
+C
+C     Lyapunov equation, orthogonal transformation.
+C
+C     *****************************************************************
+C
+C     .. Parameters ..
+      DOUBLE PRECISION  ONE, ZERO
+      PARAMETER         ( ONE = 1.0D0, ZERO = 0.0D0 )
+C     .. Scalar Arguments ..
+      DOUBLE PRECISION  B, S
+C     .. Array Arguments ..
+      DOUBLE PRECISION  A(2), C(2)
+C     .. Local Scalars ..
+      DOUBLE PRECISION  D
+C     .. External Functions ..
+      DOUBLE PRECISION  DLAPY3
+      EXTERNAL          DLAPY3
+C     .. Executable Statements ..
+C
+      D = DLAPY3( A(1), A(2), B )
+      IF ( D.EQ.ZERO ) THEN
+         C(1) = ONE
+         C(2) = ZERO
+         S = ZERO
+      ELSE
+         C(1) = A(1)/D
+         C(2) = A(2)/D
+         S = B/D
+         A(1) = D
+         A(2) = ZERO
+      END IF
+C
+      RETURN
+C *** Last line of SB03OV ***
+      END
```