Mathematical Notes
Mathematical Notes > 2001 > 69 > 3-4 > 293-297
Mathematical Notes > 2003 > 73 > 3-4 > 314-320
Mathematical Notes > 2005 > 78 > 3-4 > 437-442
Mathematical Notes > 2006 > 79 > 1-2 > 254-262
Mathematical Notes > 2013 > 94 > 5-6 > 908-912
Mathematical Notes > 2015 > 98 > 3-4 > 631-635
Mathematical Notes > 2015 > 98 > 5-6 > 847-851
Mathematical Notes > 2018 > 104 > 3-4 > 437-442