I can't use scaled coordinates with BarChart:
   'Placed::labpos: "\!\(\"0.9\"\) is not a valid position for the         placement of labels.'
     Module[{labels = {"HSTM", "SCOPUS", "ISI", "PubMed"}, 
     data = {0, 13, 39, 25}}, 
     BarChart[data, ChartLegends -> Placed[labels, {0.9,0.8}], 
     ChartStyle -> {RGBColor[0, 0, 0], RGBColor[0.8, 0, 0.2], 
     RGBColor[0.3, 0.8, 0.2], RGBColor[0, 0.3, 0.7]}, 
     PlotRange -> {{0.5, 4.5}, {0, 40}}, Ticks -> {None, None}, 
     AspectRatio -> 1.5, Frame -> {{True, True}, {True, True}}, 
     FrameLabel -> {Style["", FontSize -> 18], 
     Style["nº de publicaciones", FontSize -> 18]}, 
     FrameTicks -> {{{0, 10, 20, 30, 40}, None}, {None, None}}]]
Does anybody know how can I fix this?

Thanks in advance