If you call this with argument "unused=true" it searches for the translation strings that exist in en_US but are never used.
IMPORTANT: that can take quite a lot of time (up to 10 minutes), you need to tune the max_execution_time on your php.ini accordingly.

Duplicate strings in lang files in /home/pruebassumasoluc/public_html/dolibarr/dev/translation/../../htdocs/langs/en_US/ - 50 found

#StringFile and lines
14Typeadmin.lang (2915 - Type)
main.lang (255 - Type)
24InvoiceSubtypebills.lang (699 - Invoice Subtype)
main.lang (1340 - Invoice subtype)
31AccountancyCodecompanies.lang (311 - Accounting account)
main.lang (922 - Accounting Code)
3IdModuleadmin.lang (150 - Module ID)
modulebuilder.lang (2 - Module id)
4NoticePeriodadmin.lang (308 - Notice period)
holiday.lang (127 - Notice period)
5LanguageFileadmin.lang (418 - Language file)
modulebuilder.lang (57 - File for language)
6PriceFormatInCurrentLanguageadmin.lang (467 - Price Format In Current Language)
companies.lang (33 - Price display format in the current language and currency)
7Upgradeadmin.lang (1253 - Upgrade)
install.lang (99 - Upgrade)
8Serveradmin.lang (1265 - Server)
install.lang (44 - Server)
9DatabaseServeradmin.lang (1267 - Database host)
install.lang (47 - Database server)
10DatabaseNameadmin.lang (1268 - Database name)
install.lang (48 - Database name)
11Buyadmin.lang (1959 - Buy)
products.lang (58 - Purchase)
12Selladmin.lang (1960 - Sell)
products.lang (57 - Sell)
13ByDefaultInListadmin.lang (2185 - Show by default on list view)
categories.lang (102 - By default in list)
1LineIdaccountancy.lang (149 - Id line)
exports.lang (48 - Id of line)
2CustomerInvoicePaymentaccountancy.lang (268 - Payment of invoice customer)
banks.lang (107 - Customer payment)
15AffectedToagenda.lang (11 - Assigned to)
projects.lang (125 - Allocated to)
16Locationagenda.lang (15 - Location)
stocks.lang (42 - Location)
17ReceptionClassifyClosedInDolibarragenda.lang (73 - Reception %s classified closed)
receptions.lang (51 - Reception %s classified Closed)
18InterventionSentByEMailagenda.lang (91 - Intervention %s sent by email)
interventions.lang (47 - Intervention %s sent by email)
19DeleteTypeassets.lang (21 - Delete)
members.lang (99 - Delete)
20ShowTypeCardassets.lang (24 - Show model '%s')
members.lang (169 - Show type '%s')
21SubscriptionPaymentbanks.lang (109 - Subscription payment)
members.lang (183 - Contribution payment)
22InvoiceRefbills.lang (383 - Invoice ref.)
receiptprinter.lang (72 - Invoice ref)
23Salariesbills.lang (697 - Salaries)
salaries.lang (2 - Salaries)
25NoSupplierOrderboxes.lang (83 - No purchase order recorded)
orders.lang (88 - No purchase order)
26ShowCompanycashdesk.lang (32 - Show company)
companies.lang (327 - Third Party)
27DeleteFromCatcategories.lang (86 - Remove from tags/category)
compta.lang (308 - Remove from accounting group)
28Customercommercial.lang (4 - Customer)
companies.lang (265 - Customer)
29Prospectcommercial.lang (6 - Prospect)
companies.lang (262 - Prospect)
propal.lang (12 - Prospect)
30ShowTaskcommercial.lang (19 - Show task)
projects.lang (41 - Show task)
32ContractStatusClosedcontracts.lang (9 - Closed)
products.lang (92 - Closed)
33MinimumAmountdonations.lang (27 - Minimum amount is %s)
members.lang (212 - Minimum amount of membership payment (has priority on any default amounts that is lower))
34NewSubscriptioneventorganization.lang (122 - Registration)
members.lang (79 - New contribution)
35ExportsAreaexports.lang (3 - Exports)
other.lang (305 - Exports area)
36ExportableDatasexports.lang (7 - Exportable dataset)
other.lang (309 - Exportable data)
37AvailableFormatsexports.lang (32 - Available Formats)
other.lang (306 - Available formats)
38ChooseFileToImportexports.lang (71 - Upload file then click on the %s icon to select file as source import file...)
stocks.lang (259 - Upload file then click on the %s icon to select file as source import file...)
39MoveFieldexports.lang (76 - Move field column number %s)
other.lang (415 - Move the field %s)
40CreateUserinstall.lang (54 - Create user account or grant user account permission on the Dolibarr database)
users.lang (31 - Create user)
41CreatedByother.lang (137 - Created by %s)
ticket.lang (173 - Created by)
42Stockproducts.lang (52 - Stock)
stocks.lang (19 - Stock)
43Stocksproducts.lang (54 - Stocks and location (warehouse) of products)
stocks.lang (20 - Stocks)
44Movementsproducts.lang (55 - Movements)
stocks.lang (31 - Movements)
45Suppliersproducts.lang (97 - Vendors)
suppliers.lang (2 - Vendors)
46Unitproducts.lang (190 - Unit)
stocks.lang (49 - Unit)
47ContractSignedpropal.lang (99 - Contract signed)
recruitment.lang (48 - Contract signed)
48WithdrawalReceiptsalaries.lang (58 - Credit transfer order)
withdrawals.lang (12 - Direct debit order)
49OrderWaitingsalaries.lang (59 - Pending order)
withdrawals.lang (94 - Waiting for treatment)
50NewUserticket.lang (309 - New user)
users.lang (30 - New user)