"Brooke has her note. I have mine. They are tucked away in our briefcases; always with us, never out of reach. I found mine in the black backpack that we took to Elena’s wish trip. Brooke found her letter in the side pocket of her briefcase, where Elena had put it many months before. These are two of many letters that Elena hid for us in the last nine months of her life—some hidden between books on the bookshelf, in the corners of our dresser drawers, or between dishes in the china cabinet. Each note deliberately left professing her love for her family. They are constant reminders of her determination and her inspiration. She knew somehow that one day we would need them to continue." - Elena's Dad.
Some of Elena's Love notes found
A book about Elena's love notes and touching stories published by her parents to fund a non-profit organization The Cure Starts Now dedicated to fighting pediatric brain cancer.
Source found from here