Book  (Jan 2000)  Page(s) 236.  
 
Happy Days Hybrid Tree Peony (Saunders 1948). A semi-double yellow and red hybrid

Article (magazine)  (Jan 1955)  Page(s) 25.  
 
Varieties Raised in America. All by Professor Saunders...
The "Tea Rose Group." Generally yellow, but tinted or suffused reddish, single to double...
'Happy Days,' (1948)

Article (magazine)  (Jan 1955)  Page(s) 57.  
 
Alphabetical Check List of Tree Peony Names In  Public Collections And/or Available in Nurseries 1954-1955
Lutea hybrid, Yellow with reddish tones, 'Happy Days' (Saund. 1948), [Gardens] Scott Foundation

Magazine  (Mar 1954)  Page(s) 22.  
 
Hybrid Tree Peonies
...By far the most important work with these hybrids has been done by Prof. A. P. Saunders and his originations now number about 80. Their color range is truly remarkable. [...]
The list of hybrid tree peonies following is up to date as far as we could make it.
Originations of A. P. Saunders, Clinton, N.Y.
Hybrids of suggruticosa, lutea and Delavayi.
Happy Days, Single, small golden rose edged red. 1948.

Book  (1944)  Page(s) 104.  
 
For next year 1945
Make a master list of tree peonies to be grafted & check them off as done.
For 1944
...16420 16 [grafts]

Book  Page(s) 19.  
 
16420 "Happy Days" Single Light yellow ground ...strawberry pink....& flushing. Dark crimson onglet. Flower not large but held conspiciously. Great bloomer. Very happy looking