The pollen parent of 18.889 is (Souvenir de H.A. Verchusen x President H. Hoover). However its code number is .. wobbling (25.223 - 252.83 - 252.23)!! See the references of 18.889.
The name has to be: Souvenir de H.A. Verschuren See: http://www.helpmefind.com/rose/l.php?l=2.17004 I recognized a Dutch Breedername misspelled, so I looked that up.
You are right: I mispelt it. Unfortunatly the wobbling (25.223 - 252.83 - 252.23) of the code number of the rose Souvenir de H.A. Verschuren x President H. Hoover is not due to my misspelling.