subroutine mrseb(x,scale,mode,upv,dnv,usea,dsea,str,chm,bot,glu)
cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
c                                                                    c
c  This program returns the fitted parton distributions for MRS(A')  c
c  ... it is an analytic approximation to the "grid version" and     c
c  gives much smoother distributions. It is, however, much slower.   c
c  Full details of the fit are contained in the preprint "Pinning    c
c  Down the Gluon in the Proton", by A.D. Martin, R.G. Roberts and   c
c  W.J. Stirling, Phys. Lett. B354 (1995) 155-162,  to which         c
c  reference should be made if appropriate.                          c  
c                                                                    c
cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
      implicit real*8(a-h,o-z)
      dimension z(18,8),f(8)
      data z/
     .2.385035, -1.750356,  0.370491,  0.581567,  0.033300,  0.012245,
     .3.925280, -0.226187, -0.062425, -0.862021,  1.178930,  0.038682,
     .4.894751, -1.377950,  0.280011,  0.061201,  0.749858,  0.092008,

     .0.270620, -0.195488,  0.040248,  0.357825,  0.156226, -0.020230,
     .4.339434, -0.525551, -0.016963,  6.583414, -0.366604,  1.082098,
     .2.174049,  0.263928, -1.336412,  0.101026,  1.140400, -0.026956,

     .0.852604, -0.683552,  0.214748, -0.105954, -0.211982,  0.010073,
     .4.305152,  0.992946,  0.019575, -1.042052,  0.027041, -0.255378,
     .4.441180, -1.800216,  0.129922,  0.639220,  0.833309, -0.341173,

     .0.328730, -0.173874,  0.006988, -0.228390,  0.025648, -0.083929,
     .9.748830, -0.727386,  0.397301, -1.384145, -0.538920,  0.432677,
     .10.440065, -4.280664, 1.752318, -0.192712,  0.860909, -0.191209,

     .0.012332, -0.002796,  0.000000, -0.205990,  0.123876,  0.070738,
     .10.590572, 0.702136, -0.391293,  0.000000, 16.654520,  8.695223,
     .190.873402,-92.774861,-17.858415, -1.078797,0.650973,  0.080318,

     .0.042355, -0.025763,  0.006208, -0.117133, -0.090933, -0.031820,
     .8.486509, -1.178987,  0.706619, -1.478869,  0.416645,  0.202853,
     .12.931922, -4.845551,  0.221202,  0.563591, 0.954011, -0.329131,

     .0.001518,  0.018562, -0.005142, -0.067847, -0.212202,  0.017218,
     .5.612756,  3.786456, -2.084374, -0.140671, -3.278622,  1.815593,
     .6.910856,  0.785627, -3.351047,  1.384535, -0.069658, -0.078327,

     .-0.004515, 0.013875, -0.004472, -0.146553, -0.034326, -0.043137,
     .2.593083,  3.836694, -0.763188,  1.095127, -2.988716,  1.042826,
     .-2.628259,  7.263671, -2.674676, 1.660073,  0.206697, -0.081092/

      al=0.231
      q2=scale*scale
      q0=2.
      arg=(dlog(scale/al)/dlog(q0/al))
      s=dlog(arg)

      do 10 j=1,8

      a=z(1,j)+z(2,j)*s+z(3,j)*s*s
      b=z(4,j)+z(5,j)*s+z(6,j)*s*s
      c=z(7,j)+z(8,j)*s+z(9,j)*s*s
      d=z(10,j)+z(11,j)*s+z(12,j)*s*s
      e=z(13,j)+z(14,j)*s+z(15,j)*s*s
      h=z(16,j)+z(17,j)*s+z(18,j)*s*s 
   10 f(j)=a*x**b*(1.-x)**c*(1.+d*sqrt(x)+e*x)*(dlog(1./x))**h
      upv=f(1)
      dnv=f(2)
      glu=f(3)
      dusum=f(4)
      dudif=f(5)
      str=f(6)
      chm=f(7)
      bot=f(8)
      dsea=0.5d0*(dusum+dudif)
      usea=0.5d0*(dusum-dudif)
      if(q2.lt.2.7d0) chm=0.d0
      if(q2.lt.30.d0) bot=0.d0
      if(chm.lt.0.d0) chm=0.d0
      if(bot.lt.0.d0) bot=0.d0
      return
      end