Magazine  (2012)  Page(s) 41. Vol 34, No. 2.  
 
Eric Timewell. Frank Riethmuller’s Niece Elsie:
Most [roses] survived because Elsie took them to Toowoomba….At this point it became all too easy for her to leave behind the humiliation of those roses dedicated to women. At least seven Riethmuller roses of all sorts ‘Pearl Costin' and…. disappeared from view, in most cases never to be seen again.

Newsletter  (1995)  Page(s) 18. Vol 4, No. 4.  
 
Pearl Costin HT. 1959. F. L. Riethmuller. Elli Knab x Amy Johnson.

Book  (1963)  Page(s) 233.  
 
Pearl Costin. HT. yb (F. L. Riethmuller, ’59), ‘Elli Knab’ x ‘Amy Johnson’. Large to medium size, long pointed bud; light yellow with pink center, semi-double to double, open, cupped, large blooms borne singly and several together on long stem. Slight fragrance. Good lasting quality. Abundant, leathery, wrinkled foliage. Vigorous, upright, bushy, disease resistant, hardy growth. Intermittent blooming.

Book  (1960)  Page(s) 20.  
 
Dr. A. S. Thomas. New Rose Registrations. No. 159 . Pearl Costin H.T. F. L. Riethmuller. November 19, 1959.