− | Brevetto per una penna a sfera. Riferimenti a {{MentionPatent|US|1527971}}, {{MentionPatent|US|1805347}}, {{MentionPatent|US|1206683}}, {{MentionPatent|US|1310257}}, {{MentionPatent|US|1725064}}, {{MentionPatent|US|1590394}}, {{MentionPatent|US|1774819}}, {{MentionPatent|US|0777408}}, {{MentionPatent|US|0824733}} e {{MentionPatent|US|1156287}}. | + | Brevetto per una penna a sfera. Riferimenti a {{MentionPatent|US|777408}}, {{MentionPatent|US|824733}}, {{MentionPatent|US|1156287}}, {{MentionPatent|US|1206683}}, {{MentionPatent|US|1310257}}, {{MentionPatent|US|1527971}}, {{MentionPatent|US|1590394}}, {{MentionPatent|US|1725064}}, {{MentionPatent|US|1774819}} e {{MentionPatent|US|1805347}}. |