http://www.englisch-hilfen.de/en/exercises/reported_speech/statements.htm
http://www.englisch-hilfen.de/en/exercises/reported_speech/statements2.htm
http://www.perfect-english-grammar.com/reported-speech-exercise-1.html
http://www.perfect-english-grammar.com/support-files/reported_statements.pdf
https://www.ego4u.com/en/cram-up/grammar/reported-speech/exercises?04
https://elt.oup.com/student/solutions/int/grammar/grammar_06_012e?cc=global&selLanguage=en
http://a4esl.org/q/h/9901/tm-reported1.html
http://www.english-4u.de/rep_speech_ex1.htm
http://www.kico4u.de/english/uebungen/reportedspeech/statements.htm