Krishna Book
This is the book that contains this famous prayer: O Lord Kṛṣṇa, at this moment let the royal swan of my mind enter the tangled stems of the lotus of Your feet. How will it be possible for me to remember You at the time of death, when my throat will be choked up.
Mukunda Mala Stotra by Kulasekhara Acharya
In the Bhagavad Gita the soul is described as immortal. Yet this other important scripture talks of the "killer of the soul".
Sri Isopanishad
"Always remember Krishna and never forget Him" is quoted by Rupa Gosvami in Caitanya Caritamrta from this scripture.
Padma Purana