Changes made to Sample3_modified.fo:

1. font-style="bold": invalid property value. Replaced with 
   font-weight="bold".

2. It is illegal to place text directly into 
   fo:block-container: it only accepts block-level
   children. Wrapped the respective text into 
   <fo:block>...</fo:block>
   
3. Size of the absolutely positioned block container 
   is left underspecified. The behaviour in this situation
   is not constrained by the XSL Reocmmendation. XEP behaves
   as if all missing position traits (in this case, 'right'
   and 'bottom') were set to 0. This makes the contents
   of the block container overlap with the rest of the text.
   To fix it, 'right' and 'height' attributes were
   added to the block-container.