For example, I found Matys to also be written as Matyz. I found Kurenda recorded as Korenda and Skrabalak as Skrbalik. Hruszczak was changed to Ruczhak when my grandfather started school and the teacher Americanized his name so it was easier on her. One of his brothers switched the c and the z around. On top of that it is also pronounced differently depending on who you ask! I have also seen Hruszczak butchered by a few census recorders.
Recently, someone (on Facebook) suggested an article by William F. Hoffman. He wrote this excellent article about the mutilation of Eastern European surnames.