The following publications describe in detail the importance of Boutens and the Boutens Collection:

De P.C. Boutens-collectie van de Zeeuwse Bibliotheek te Middelburg (The P.C. Boutens Collection of the Zeeland Library in Middelburg) / compiled and introduced by R.M. Rijkse; with contributions from B. Peperkamp and M. Goud. - Amsterdam: Schiphouwer en Brinkman, 1997.

Bijzondere collecties in openbare bibliotheken (Special collections in public libraries) / Erna Slangen. - [The Hague] [etc.] : Association of Public Libraries [etc.], cop 2006.

‘Ik heb iets bijna schoons aanschouwd’: over leven en werk van P.C. Boutens 1870-1943 (I beheld something almost beautiful: on the life and works of P.C. Boutens 1870-1943) / ed. Jan Nap ... [et al.]; selection and captions by Murk Salverda. – The Hague [etc.]: Literary Museum and Documentation Centre [etc.], 1993.
Note: the full text maybe viewed online.

Dichters die nog maar namen lijken (Poets who seem just names) / A.L. Sötemann. - Amsterdam [etc.]: Meulenhoff [etc.], cop 2003. Compilation of papers that had previously appeared in the magazine Ons erfdeel (Our Heritage).