Magazine  (Jan 2011)  Page(s) 4.  
 
[Back-Translation of "A Persian Story" by Chris Warner, translated into Dutch by Els de Krijger]
After years of struggling together with Alec Cocker, Jack Harkness lectured to the Royal National Rose Society (RNRS) in 1976 about their results with the persica crosses. I was present at that lecture and got completely excited by his story. Afterwards Jack offered some hybrids for sale for the "giveaway" price of £ 250 for 5 plants. As a young and underpaid teacher this was way above my budget, but in 1982 the price had dropped and I bought 'Tigris' (H. persica x 'Trier'). 
The first persica hybrids only flowered once a year for a very short period of time and were quite sensitive to black spot.

Book  (2010)  Page(s) 92.  
 
Peter Harkness. An Update on Persica Hybrids.
....it was decided to introduce four of them, rather than see them perhaps lost for ever.
Tigris [HARprier] (R. persica x 'Trier') was pollinated in 1975 and introduced in 1985, and bears small, canary yellow double rosettes with deep red petal 'eyes' on a low compact plant.

Book  (1996)  Page(s) 82.  
 
Tigris (HARprier) Persica hybrid... canary yellow double rosettes with red eye at petal bases... Parentage: R. persica x 'Trier'. Harkness (England) 1985.

Book  (1996)  Page(s) 52.  Includes photo(s).
 
Tigris (HARprier) Persica hybrid shrub... one of a few varieties successfuly bred from [R. persica]... Harkness 1985

Book  (1993)  Page(s) 65.  Includes photo(s).
 
[Listed under "Wild Roses and Their Cultivars"] One of the three hybrids (the others are 'Euphrates' and 'Nigel Hawthorne') which have been introduced since 1968 when Alec Cocker and Jack Harkness in Britain obtained seeds of Rosa persica and started a breeding programme to try to raise roses with a red eye.

Book  (1988)  Page(s) 8.  
 
[In his foreward to this book, Peter Hering writes:] 'Tigris' and 'Euphrates' … have been created by crosses with Rosa (or Hulthemia) persica, a strange plant that has sometimes been included with the Rose family and sometimes put in a genus of its own. Work with persica is difficult and has rarely been attended with any success. These two varieties represent a very significant accomplishment for Harkness & Co.

Book  (1985)  Page(s) 166.  
 
The most interesting project was Rosa persica, a difficult species, of which I probably held the largest stock ever grown outside its native regions. The object here was to raise a fertile hybrid, but although we got in the end over a hundred, some very beautiful, and notable as the first recorded since 1836, they were all sterile and bloomed only in the summer. Their beauty lay in a dark red eye at the centre of the bloom. I obtained them single and double, yellow, pink, salmon and orange. Having put a lot of work into this bit of pioneering, I thought we might introduce two of the hybrids, and sent them to the Royal National Rose Society's trials. No interest was expressed, and I accepted the fact that they were not yet suitable for gardens, although of great botanical interest.