Bd. 1. 1852
http://books.google.com/books?id=JjACAAAAQAAJ
https://archive.org/details/populareducator02educgoog
http://purl.ox.ac.uk/uuid/d4947108e2384e4592d00d5b8cbcc3ac
Bd. 2. 1852
http://books.google.com/books?id=JjACAAAAQAAJ&pg=PA429
https://archive.org/stream/populareducator02educgoog#page/n430
http://purl.ox.ac.uk/uuid/d4947108e2384e4592d00d5b8cbcc3ac
Bd. 3. 1853
http://books.google.com/books?id=xF_BIl4thRkC
http://hdl.handle.net/2027/mdp.39015013167872
Bd. 4. 1854
http://books.google.com/books?id=vsX_1qvT3J0C
http://books.google.com/books?id=lTACAAAAQAAJ
https://archive.org/details/populareducator00educgoog
http://hdl.handle.net/2027/mdp.39015033370159
http://purl.ox.ac.uk/uuid/5d6d466701994dfe981fa55231c1bb6f
Bd. 5. 1854
http://books.google.com/books?id=SDgCAAAAQAAJ
https://archive.org/details/populareducator01educgoog
http://purl.ox.ac.uk/uuid/6b48b5a1b12042769894fe265b2a073a
Bd. 6. 1855
http://books.google.com/books?id=mXFMAAAAMAAJ
http://hdl.handle.net/2027/mdp.39015013167880
http://purl.ox.ac.uk/uuid/6b48b5a1b12042769894fe265b2a073a
Bd. 1. 1852
http://books.google.com/books?id=JjACAAAAQAAJ&pg=PR3
Bd. 2. 1852
http://books.google.com/books?id=JjACAAAAQAAJ&pg=PA431
Bd. 3. 1853
http://hdl.handle.net/2027/mdp.39015013167872?urlappend=%3Bseq=7
Bd. 4. 1854
http://hdl.handle.net/2027/mdp.39015033370159?urlappend=%3Bseq=7
Bd. 5. 1854
http://books.google.com/books?id=SDgCAAAAQAAJ&pg=PP15
Bd. 6. 1855
http://hdl.handle.net/2027/mdp.39015013167880?urlappend=%3Bseq=7
Wikipedia, engl.
http://en.wikipedia.org/wiki/John_Cassell