1 General Part
CHAPTER VI- DETERMINATION OF PUNISHMENT
Article 56- Joining of sentences
If before serving the full sentence, the convicted is sentenced for a criminal act committed prior to the sentencing, the rules of the previous article shall apply, and the already served portion will be calculated into the new sentence.
When the convicted commits a new criminal act after his sentencing, but before the full term of the sentence is served, the court joins the new sentence with the remaining portion of the previous term, according to the rules provided for in Article 55 of this Code.
Joint sentence following multiple convictions - national proceedings
EDIT.