MR0216153
Ak{\^o}, Kiyoshi
Kiyoshi AKÔ
A new construction of barrier functions
Funkcialaj Ekvacioj. Serio Internacia
9
1966
1--7
http://fe.math.kobe-u.ac.jp/FE/Free/vol09/fe09-7.pdf
http://fe.math.kobe-u.ac.jp/FE/FE_pdf_with_bookmark/FE01-10-en_KML/fe09-001-007/fe09-001-007.pdf
http://www.ams.org/mathscinet-getitem?mr=MR0216153
fe09-001-007
1966
A New Construction of Barrier Functions
Ak{\^o}, Kiyoshi
Ak{\^o}, Kiyoshi