Barking Toad found in Coal in Hartlepool (sources)
- "An Extraordinary Toad," article in Zoologist: a monthly journal of natural history, Volume 23, 1865 London. Pg. 9630. Online at: https://books.google.com/books?id=d482AQAAMAAJ&pg=PA9630&lpg=PA9630&dq=%22an+extraordinary+toad%22&source=bl&ots=cBkAcr1EqM&sig=BDPxF2sqcqqyyCayAjkFf3TYzQY&hl=en&sa=X&ei=asb0VJqjAdPmoATIhIDYDA&ved=0CB8Q6AEwAA#v=onepage&q=%22an%20extraordinary%20toad%22&f=false
- The Swiss Cross: a monthly magazine of popular science, Vol. V, No. 1, January, 1889 New York, USA. Pg. 20. Online at: https://books.google.com/books?id=tEUoAQAAIAAJ&pg=PA20&dq=Swiss+cross+monthly+hartlepool&hl=en&sa=X&ei=_8b0VKbcCYa4oQTh_oGABw&ved=0CCsQ6AEwAA#v=onepage&q&f=false