Der Schlüssel; or, Key to German tresor.
Being a literal translation of the above work for easily turning English compositions into German at sight.
By Louis Philippe R.F. de Porquet.

APA Citation

Fenwick de Porquet, L. Philippe R. (1846). Der Schlüssel; or, Key to German tresor: Being a literal translation of the above work for easily turning English compositions into German at sight. London: Fenwick de Porquet.

MLA Citation

Fenwick de Porquet, Louis Philippe R. Der Schlüssel; Or, Key to German Tresor: Being a Literal Translation of the Above Work for Easily Turning English Compositions Into German At Sight. London: Fenwick de Porquet, 1846.

Warning: These citations may not always be complete (especially for serials).