4 September – Saint Ida of Herzfeld

Bei der Jagd sucht ein Hirsch Zuflucht bei Ida
Shrine

Modern Hagiography

Bibliotheca Sanctorum

Martyrologium Romanum

Dictionary of Saintly Women

Lives of the Saints by Alban Butler.

Lives of the Saints by Sabine Baring-Gould.

Our Birthday Bouquet Culled from the Shrines of the Saints and the Gardens of the Poets by Eleanor C. Donnelly.

Pictorial Half Hours with the Saints by Auguste François Lecanu.

Medieval Hagiography

BHL 

Acta Sanctorum

Art & Architecture

Ida-Schrein in Herzfeld, details (archived)

Wikimedia Commons

Customs & Devotions

Ida-Woche

Ida-Auenweg in den Lippeauen

4 September – Saint Marcellus of Chalon

Modern Hagiography

Bibliotheca Sanctorum

Martyrologium Romanum

Roman Martyrology

Lives of the Saints by Alban Butler.

Lives of the Saints by Sabine Baring-Gould.

La vie des saints

Medieval Hagiography

BHL

Acta Sanctorum

The Cult of Saints in Late Antiquity Database

Art & Architecture

Portail Biblissima

POP : la plateforme ouverte du patrimoine

Saints and their Attributes

The Saints in Art by Joseph Maria von Radowitz.

Emblems of Saints by Which They Are Distinguished in Works of Art by F. C. Husenbeth.

Music

Medieval Music Database

Cantus: A Database for Latin Ecclesiastical Chant

3 September – Saint Seraphia

Annus Dierum Sanctorum
Non omnes capiunt verbum hoc.
All men take not this word.
  Matthew 19.11

Modern Hagiography

Bibliotheca Sanctorum

Roman Martyrology

Dictionary of Saintly Women

Lives of the Saints by Francis Weninger.

Character Calendar 

Pictorial Lives of the Saints

Our Birthday Bouquet Culled from the Shrines of the Saints and the Gardens of the Poets by Eleanor C. Donnelly.

Victories of the Martyrs by Saint Alphonsus Liguori.

Medieval Hagiography

BHL, Supplement

The Cult of Saints in Late Antiquity Database

Art & Architecture

Décollation de sainte Sérapie (France, Valenciennes. Bibliothèque municipale, Ms. 838 f. 105v)

Saints and their Attributes

The Saints in Art by Joseph Maria von Radowitz.

Emblems of Saints by Which They Are Distinguished in Works of Art by F. C. Husenbeth.