Changes made to Sample4_modified.fo:

1. All occurrences of 'keep-together' are replaced by 
   'keep-together.within-column'. Otherwise, line breaks 
   are disabled in the element that bears the property. 
   This happens because keep-together="always" is equivalent 
   to setting three individual components:
   
       keep-together.within-line="always" 
       keep-together.within-column="always" 
       keep-together.within-page="always" 
       
   It is the first components that disables line breaks.
   
2. Image sizes in the original file are equal to the sizes
   of block containers that include them. However, the block
   with an image inside also has half-leading white space
   before and after the image; as a result, the image does 
   not fit. To remove white space, all images are wrapped
   into the following:
   
   <fo:block line-height="0pt" font-size="0pt">...</fo:block>