It may be simple. Though I can't read Dutch, I can help you. 
 If you want to directly add relevant sources to "Martha Gellhorn", you had better get the English-language book, "Travels with myself and another". And add the source to the sentence concerned, using  and Template:Cite book(in Dutch, nl:Sjabloon:Citeer boek) like below:  
{{cite book
| last                  = Gellhorn
| first                 = Martha
| authorlink            = Martha Gellhorn
| title                 = Travels with Myself and Another: A Memoir
| trans_title           = 
| url                   = http://www.us.penguingroup.com/nf/Book/BookDisplay/0,,9781585420902,00.html
| accessdate            = 
| edition               = 
| date                  = 
| origyear              = 
| year                  = 
| month                 = 
| publisher             = 
| location              = 
| language              = 
| isbn                  = 
| id                    = 
| page                  = 
| pages                 = 
| chapter               = 
| trans_chapter         = 
| quote                 = 
| layurl                = http://www.amazon.com/Travels-Myself-Another-A-Memoir/dp/1585420905/ref=sr_1_1?ie=UTF8&qid;=1368102719&sr;=8-1&keywords;=Travels+with+myself+and+another
}}

 There is a way to indirectly reflect your source(your Dutch book) to "Martha Gellhorn". First, you need go to the section concerning her attitude to Stalin or Stalin's communism in the article ":nl:Martha Gellhorn" and make the sentence sourced as mentioned above, showing the Dutch title("Travels with myself and another"?), the chapter name 'Een blik op Moedertje Rusland', the pages(p. xy or pp. xy - xz) of your source, and so on. ISBN is preferable. Quote is possible and helpful for readers. Basically, English templates are available in any Wikipedia. 
 After editing nl:Martha Gellhorn, see the left side bar, (click "Hulmpmiddelen",) and click "Permanente Kooppeling". You can get the "oldid=XXXXXXXX" of the page from the address bar. 
 Second, you need come to the section concerning her attitude to Stalin or Stalin's communism in the article "Martha Gellhorn" and edit. 
 And before you click "Save page", enter "From [[:nl:Martha Gellhorn]] as of revision (date,month,year,time,)..." into "Edit summary".
 After editing Martha Gellhorn, see the left side bar, (click "toolbox", and click "Permanent link". You can get the "oldid=YYYYYYYYYY" of the page from the address bar. 
 Third, you need announce in the article talk page(Talk:Martha Gellhorn) that you translated from the Dutch Wikipedia. You have to make a new section and place this Template:translated page, that is, {{translated page| nl | Martha Gellhorn | version = XXXXXXXX | insertversion = YYYYYYYYYY | section = ?Political and religious views }}. 
 For more information, see Wikipedia:Copying within Wikipedia#Translating from other language Wikimedia Projects and Template:translated page. 
 Probably, you have to click "undo" button, too, because there seems to be (anti-Jewish, anti-Orchestra, anti-music, anti-democracy, anti-human-rights, anti-freedom) admins who are crazy about disruptive personal-attack-reverting, as you know.-1335, -1258 personal-attacking-revert by ADMINS
 ADMINS stalking me,  repeated personal-attack-reverting my edits disruptively ( -28, -214, -448, -520, -790 by ADMINS ).  ADMINS threatening criminally, have abused me by blocking. ADMINS have managed to damage me, not caring what anybody thought. Maybe, thus, ADMINS have dameged non-adminl Wikipedians and Wikipedia itself unfairly, intensively, and extensively (like Nazis). Probably I have to go into exile. So, please don't think I can edit for you. Do it yourselef. Don't trust Wikipedia:Administrators. Good luck.