Mines can be laid in many ways : by purpose-built minelayers , refitted ships , submarines , or aircrafta '' and even by dropping them into a harbor by hand .
Mines can be laid in many ways : by specially built minelayers , refitted ships , submarines , aircraft , or even by dropping them into a harbor by hand .
Mines can be laid in many ways : by specially built minelayers , refitted ships , submarines , aircraft , or even by dropping them into a harbor by hand .
Usar una redacción más simple: Mines can be laid in many ways : by purpose-built minelayers , refitted ships , submarines , or aircrafta '' and even by dropping them into a harbor by hand . Producción: