A comparison of hesychasm and other traditions by Dr. Thomas Mether
This is an excellent article for understanding why contemplative traditions have so much in common.
Real and unreal divine union by Archimandrite Sophrony
An enlightened yoga adept who became the student of St. Silouan of Mt. Athos
Buddhism and Conversion to Orthodoxy - Q & A with Fr. John Matusiak
"Christian Zen, Christian Yoga, and Other Borrowed Practices
From the book "Orthodoxy and the Religion of the Future. Written during the crazier '70s, much of this still applies to our time.
Unreal Christian contemplative practices by Fr. Seraphim Rose
(A shorter quote from the book above)
Fr. Seraphim's writings are hard-hitting, but stand the test of Patristic discernment which is greatly lacking in our time. Do not be merely put off by Fr. Seraphim's statements, but get the essence of what is being said.
The vast gap between "Spiritualities" by Metropolitan Hierotheos Vlachos
Epilogue from "The Psychological Basis of Mental Prayer in the Heart" by Fr Theophanes
The whole book should be read, but this epilogue which summarizes key points of the book also sheds light on these topics.