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(G)   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/
     .1.665297, -0.590753,  0.086807,  0.676836, -0.027729,  0.006186,
     .3.340307,  0.260426,  0.024214, -0.787023,  1.101313, -0.302934,
     .6.098057, -2.645910,  0.175731,  0.557278,  0.363394, -0.001549,

     .0.171268, -0.086429,  0.012191,  0.388998,  0.139088, -0.014565,
     .4.049580, -0.495801,  0.071001,  8.829433,  0.246082, -0.319317,
     .5.310913, -6.033850,  1.335430,  0.391294,  0.974633, -0.026356,

     .1.121933, -0.980891,  0.250001, -0.279071, -0.118949,  0.001370,
     .5.733053,  0.962694, -0.537345, -4.338513,  4.055084, -1.249222,
     .11.591153, -9.385871,  2.080363, 0.233747,  0.649513, -0.033386,

     .0.811684, -0.732591,  0.188398, -0.146012, -0.450745,  0.162278,
     .10.716037,  0.423859, -0.332372, -3.347546, 1.476767, -0.164336,
     .10.221619, -2.432161,  0.693669, -0.372843, -0.451730, 0.548307,

     .0.018819, -0.019057,  0.014581,  0.473385, -0.026701, -0.191575,
     .8.942582, -0.562553,  2.098186, -1.302327, 29.018376,-11.868145,
     .105.320622,-53.953297,  1.329035, 0.878000, 0.499894, -0.971650,

     .0.093684, -0.074091,  0.033660, -0.107765, -0.408746,  0.100063,
     .9.275198,  0.692364,  0.110208, -2.787409,  0.041578,  0.488094,
     .10.637883, 3.815478, -4.848576,  0.184162,  0.185983, -0.186796,

     .0.001026,  0.015587, -0.001414, -0.111311, -0.346509,  0.094542,
     .5.764679,  4.958334, -2.102611, -1.341127, -2.951861,  1.855254,
     .12.079860, -0.297841, -3.809543, 1.480855, -0.719267,  0.175987,

     .-0.001533,  0.004429, -0.000718, -0.097267, -0.221771, 0.056117,
     .3.630148,  2.941006, -0.512863, -0.483095,  1.599856, -1.197675,
     .8.366443, -4.004534,  1.022508,  2.526478, -0.713666,  0.277209/

      al=0.254
      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