<ref>[https://worldwide.espacenet.com/publicationDetails/originalDocument?CC=CA&NR=38933A&KC=A&FT=D&ND=3&date=18920512&DB=&locale=en_EP# Akroyd & Binney patent CA38933]</ref> | <ref>[https://worldwide.espacenet.com/publicationDetails/originalDocument?CC=CA&NR=38933A&KC=A&FT=D&ND=3&date=18920512&DB=&locale=en_EP# Akroyd & Binney patent CA38933]</ref> |