− | Brevetto per una penna a sfera. Riferimenti a {{MentionPatent|US|641503}}, {{MentionPatent|US|807280}}, {{MentionPatent|US|1177631}}, {{MentionPatent|US|2408256}}, {{MentionPatent|US|2425198}}, {{MentionPatent|US|2427068}}, {{MentionPatent|US|2432061}}, {{MentionPatent|US|2444003}} e {{MentionPatent|US|2444004}} ed inoltre {{MentionPatent|GB|GB476971}}. | + | Brevetto per una penna a sfera. Riferimenti a {{MentionPatent|US|641503}}, {{MentionPatent|US|807280}}, {{MentionPatent|US|1177631}}, {{MentionPatent|US|2408256}}, {{MentionPatent|US|2425198}}, {{MentionPatent|US|2427068}}, {{MentionPatent|US|2432061}}, {{MentionPatent|US|2444003}} e {{MentionPatent|US|2444004}} ed inoltre {{MentionPatent|GB|476971}}. |