Mona Lisa Underdrawing Researchers Discover a Hidden Drawing Behind 'Mona Lisa

No, this isn’t the plot of a Nicolas Cage movie. A special camera went deep into the famous painting
A special camera went deep into the famous painting's nooks and crannies. 

PDF) Leonardo, Mona Lisa and La Gioconda: Reviewing the Evidence

A NEW WAY OF LOOKING AT THE MONA LISA, monalisa

The Mona Project: 2010

Mona Lisa': Hidden portraits 'found underneath

Is There a Hidden Drawing Beneath the 'Mona Lisa'?, monalisa

Hidden Drawing Discovered Beneath 'Mona Lisa, monalisa

And she just keeps on smiling

Researchers Have Discovered a Hidden Drawing Behind 'Mona Lisa

The Challenges of a Leonardo Attribution - The Mona Lisa Foundation